To see the other types of publications on this topic, follow the link: Plants Plant physiology. Plants Plants. Plantes.
Dissertations / Theses on the topic 'Plants Plant physiology. Plants Plants. Plantes'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Plants Plant physiology. Plants Plants. Plantes.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Lucas, W. J. "Plant physiology : transport processes in plants /." Title page, preface and contents only, 1989. http://web4.library.adelaide.edu.au/theses/09SD/09sdl933.pdf.
Full textAbstract:
Thesis (D. Sc.)--Faculty of Science, University of Adelaide, 1990.Published works [representing] original research conducted during the various phases of [his] academic development--Pref. Includes bibliographical references.
2
au, A. Mccomb@murdoch edu, and Arthur James McComb. "Plants and the environment." Murdoch University, 2006. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20070828.135211.
Full text
3
Wied, Anna. "Conspecific nurse effects and the evolution of monocarpy in plants /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9841363.
Full text
4
Ingarfield, Patricia Jean. "Effect of water stress and arbuscular mycorrhiza on the plant growth and antioxidant potential of Pelargonium reniforme Curtis and Pelargonium sidoides DC." Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2794.
Full textAbstract:
Thesis (MTech (Horticulture))--Cape Peninsula University of Technology, 2018.Pelargoniums have been studied extensively for their medicinal properties. P. reniforme and P. sidoides in particular are proven to possess antimicrobial, antifungal and antibiotic abilities due to their high antioxidant potential from compounds isolated from their tuberous roots. These plants have now been added to the medicine trade market and this is now causing concern for conservationists and they are generally harvested from the wild populations. This study evaluated the effect of water stress alone and in conjunction with arbuscular mycorrhiza on two species of Pelargoniums grown in a soilless medium. The experiment consisted of five different watering regimes which were applied to one hundred plants of each species without inoculation with arbuscular mycorrhiza and to one hundred plants of each species in conjunction with inoculation with AM. All the plants in the experiment were fed with a half-strength, standard Hoagland nutrient solution at varying rates viz. once daily to pot capacity, every three days to pot capacity, every six days to pot capacity, every twelve days to pot capacity and every twenty-four days to pot capacity. The objectives of the study were to measure the nutrient uptake, SPAD-502 levels (chlorophyll production) and metabolite (phenolics) formation of both species, grown under various rates of irrigation and water stress, as well with or without the addition of arbuscular mycorrhiza at planting out. Each treatment consisted of 10 replicates. SPAD-502 levels were measured weekly using a hand held SPAD-502 meter. Determination of nutrient uptake of macronutrients N, K, P, Ca, Mg and Na and micronutrients Cu, Zn, Mn, Al and B were measured from dry plant material at the end of the experiment by Bemlab, 16 Van Der Berg Crescent, Gants Centre, Strand. Plant growth in terms of wet and dry shoot and root weight were measured after harvest. Determination of concentrations of secondary metabolites (phenolic compounds) were assayed and measured spectrophotometrically at the end of the experiment. The highest significant reading of wet shoot weight for P. reniforme was taken in treatments 1 and 2 with and without mycorrhiza i.e. WF1, WF1M, WF2 and WF2M, with the highest mean found in WF1 with no mycorrhiza. This indicates that under high irrigation AM plays no part in plant growth, possibly due to leaching. More research is necessary in this regard. With regard to wet root weight, this was found to be not significant in any of the treatments, other than the longest roots being found in WF4. Measurements for dry root weight showed that WF1,2,3 and 5 were the most significant at P≤ 0.001 significance, with the highest weight found at treatment being WF3 and WF3M. The highest mean of shoot length of the plants was measured in treatment WF2 at moderate watering, but no statistical difference was found with water application and mycorrhiza addition. Nutrient uptake was increased in P. sidoides in all the different watering levels in the experiment except in the uptake of Mg. AM inoculation showed an increase in the uptake of Ca, while absorption of N occurred at higher water availability. K uptake was enhanced by the addition of AM in high water availability and K utilisation decreased as water stress increased. Medium to low watering resulted in higher leaf content in P. sidoides while the interaction between water availability and AM inoculation increased chlorophyll production towards the end of the experiment.
5
Mohamed, Fatheya. "Mineral analysis and proximate composition of leaves of (Brassica oleracea var. acephala) in response to boron application in pot experiments." Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2793.
Full textAbstract:
Thesis (MTech (Agriculture)--Cape Peninsula University of Technology, 2018.Choumollier (narrow-stem kale) (Brassica oleracea, L.) has been progressively used in recent years as a supplementary forage harvest in many countries with a temperate climate. Boron (B) and calcium (Ca) are the two most important elements for supporting plant structure and function of plasma membranes. Boron nutrition is vital for obtaining high quality yields in vegetables. The main objective of this study was to evaluate the extent to which boric acid concentration can affect growth parameters (plant height, leaf numbers, chlorophyll levels, and leaf size) of Brassica olereacea var. acephala at different stages of growth and development. Treatment comprised of four concentrations of boron (0.3 mg/kg, 0.4 mg/kg, 0.5 mg/kg and 0.6 mg/kg). Yield and physiological growth responses were measured during the course of the study to ascertain effectiveness and influence of boron treatments on the test crops. Leaves of B. oleracea were harvested at weekly intervals (W1, W2, W3, W4 and W5) after each treatment regimen for approximate basic mineral analysis and composition. Soil pH did not vary much among the various orchard blocks tested, regardless of soil depth. Exchangeable cations Na+ and K+ levels did not vary significantly, but Ca2+ and Mg2+ levels fluctuated considerably among orchards analyzed. The Control Orchard exhibited a higher P content than the other orchards. Ca, Mg, Cu and B levels did not vary significantly among the orchards, but Na, Fe and Zn levels were markedly raised in the Orchard treated with 0.3 mg/kg boron) relative to the Control Orchard. Chlorophyll fluorescence was significantly dependent on the treatment dose of boron as compared to control. Chlorophyll fluorescence also increased significantly with the growth period, i.e., the duration following the initial treatment at all doses of boron. Boron at all did not significantly affect leaf count, leaf length and plant height. The work may add to the body of knowledge on the influence of boron on the physiological performance, mineral contents and proximate composition of leaves of the species. Furthermore, the findings may have important applications in achieving high quality yields in vegetable crops.
6
Nguyen, Thi Ngoc nga. "Functional expression of Plant Defensins type 1 for zinc tolerance in plants." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20032/document.
Full textAbstract:
Plant Defensins type 1 (PDF1) sont principalement décrites pour leur rôle dans l'immunité innée en réponse à des attaques pathogènes via l'activation de la voie de signalisation de l'éthylène (Et) et de l'acide jasmonique (JA). Les défensines PDF1 du genre Arabidopsis sont également impliquées dans la tolérance cellulaire au zinc chez la levure. In planta, de nombreux résultats mettent en évidence une corrélation entre la forte accumulation des transcrits AhPDF1 et leur contribution dans la tolérance à un excès de zinc. Dans cette étude, l'analyse du transcriptome (qRT-PCR) révèle que les paralogues PDF1s, aussi bien chez A. thaliana que chez A. halleri sont très peu voire pas du tout sensibles au zinc. Toutefois, il y a une spécialisation des PDF1s en réponse à l'activation de la voie de l'acide jasmonique dans le genre Arabidopsis. De plus, la contribution fonctionnelle des membres de la famille PDF1s dans la tolérance au zinc a été caractérisée chez A. thaliana à l'aide d'une approche génétique combinant des mutants KO après insertion d'un ADN-T et la technologie de miRNA artificiel. L'étude de ces mutants souligne par ailleurs la diversité fonctionnelle au sein de la famille des défensines AtPDF1s qui ne confèrent pas toutes la tolérance au zinc. En effet, une diversité de déterminants moléculaires des PDF1s a été mise en évidence lors de cette étude. La forte accumulation des PDF1s n'est pas l'unique paramètre requis pour la tolérance au zinc. Il faut également considérer la spécificité de tissu où s'expriment ces PDF1s. A ces considérations s'ajoutent aussi des régulations post-transcriptionnelles et post-traductionnelles. L'étude de ces modifications est envisagée afin de comprendre la contribution des différentes défensines PDF1s dans la tolérance au zincPlant Defensin type 1 (PDF1s) are mainly recognized for their response to pathogen attack via ethylene (Et)/jasmonate (JA) signaling activation pathway. However, PDF1s originating from Arabidopsis genus also showed their capacity to induce cellular zinc tolerance up on expression in yeast. In planta, a group of observation highlighted the correlation of AhPDF1 high transcript accumulation for their contribution to zinc tolerance. Here, transcriptomic analysis (qRT-PCR) revealed that in both A. thaliana and A. halleri species, PDF1 paralogues were barely or not at all responsive to zinc. Nevertheless, there is a species specialization of PDF1s in response to activation of JA-signaling in Arabidopsis genus. In addition, in A. thaliana, the functional contribution of PDF1 members in zinc tolerance was investigated through genetic approach. Examining combination of T-DNA insertion knockout mutant and artificial miRNA, these studies were first direct demonstration of the functional involvement of AtPDF1s in zinc tolerance. These also highlighted the functional diversity among AtPDF1s because not all of them could play a role in zinc tolerance. Indeed, a diversity of PDF1 molecular determinants for zinc tolerance in plants was underlined. Remarkably, PDF1 high transcript is not the only important parameter for zinc tolerance and PDF1 tissue specificity could be an important factor to consider. Moreover, post-transcriptional and post-translational regulation might occur. Studies on these modifications are now the further questions in order to understand the contribution of the different PDF1s to zinc tolerance
7
Hanes, Scott Burton Wright Amy Noelle. "Organic matter type affects growth and physiology of native plants planted above-grade." Auburn, Ala, 2009. http://hdl.handle.net/10415/1895.
Full text
8
Willett, Deanna Allyn. "Temperature-regulated proteins in plants." Thesis, The University of Arizona, 1999. http://hdl.handle.net/10150/291647.
Full textAbstract:
Studies in this thesis concern expression of one class of small HSPs (sHSPs) in field grown desert plant species and the isolation of a new HSP gene encoding an sHSP targeted to plant mitochondria. Expression of class I, cytosolic sHSPs was assessed in three desert species: Screwbean Mesquite, Baja Fairyduster, and Sweet Acacia. Total leaf protein, and if available, flower and pod protein, was extracted from samples and analyzed by SDS-PAGE and Western blotting. Sweet Acacia showed strong sHSP expression in leaves with an apparent diurnal pattern of increased expression in the hotter PM. Screwbean Mesquite pods showed significant sHSP expression, which was not correlated to temperature. The isolation and sequence analysis of a gene encoding a mitochondrion-localized sHSP from Arabidopsis was completed. Comparisons to other plant sHSPs verified it was most similar to other mitochondrial-localized sHSPs from plants.
9
Stoltz, Eva. "Phytostabilisation : use of wetland plants to treat mine tailings." Doctoral thesis, Stockholm : Department of Botany, Univ, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-299.
Full text
10
Na, Jong Kuk. "Genetic approaches to improve drought tolerance of tomato and tobacco." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1127245631.
Full textAbstract:
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xv, 104 p.; also includes graphics (some col.). Includes bibliographical references (p. 93-104). Available online via OhioLINK's ETD Center
11
Ayeni, Olutoyosi Olaide. "Growth responses within the Genus Cyperus exposed to aluminium and iron in hydroponics." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2430.
Full textAbstract:
Thesis (DTech (Environmental Health))--Cape Peninsula University of Technology, 2016.Generally, aluminium (Al) is required as a micronutrient by plants. The metabolism of Al within the plant can exert a number of effects within the plant. These include: interfering with cell division in both root tips and lateral roots, increasing cell wall rigidity, maintaining the correct cellular redox state, as well as the various other physiological and growth responses. Al is one of the most abundant elements in the earth’s crust and becomes toxic in many plants when the concentration is greater than 2-3 ppm, where the soil has a pH<5.5. Iron (Fe) is an equally important element, and the toxicity of this metal possesses constraints primarily on wetland plants growing in acidic soils that have high reducible iron content. The impact of metal toxicity (Al and Fe) requires an understanding of many aspects related to Al and Fe uptake, transport and distribution by plants in wetland ecosystems. In this study, three species of Cyperus viz. Cyperus alternifolius, Cyperus prolifer and Cyperus textilis were used to carry out phytotoxicity tests to monitor xenobiotic substances.
12
Fritioff, Åsa. "Metal accumulation by plants : evaluation of the use of plants in stormwater treatment." Doctoral thesis, Stockholm University, Department of Botany, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-613.
Full textAbstract:
Metal contaminated stormwater, i.e. surface runoff in urban areas, can be treated in percolation systems, ponds, or wetlands to prevent the release of metals into receiving waters. Plants in such systems can, for example, attenuate water flow, bind sediment, and directly accumulate metals. By these actions plants affect metal mobility. This study aimed to examine the accumulation of Zn, Cu, Cd, and Pb in roots and shoots of plant species common in stormwater areas. Furthermore, submersed plants were used to examine the fate of metals: uptake, translocation, and leakage. Factors known to influence metal accumulation, such as metal ion competition, water salinity, and temperature, were also examined. The following plant species were collected in the field: terrestrial plants – Impatiens parviflora, Filipendula ulmaria, and Urtica dioica; emergent plants – Alisma-plantago aquatica, Juncus effusus, Lythrum salicaria, Sagittaria sagittifolia, and Phalaris arundinacea; free-floating plants – Lemna gibba and Lemna minor; and submersed plants – Elodea canadensis and Potamogeton natans. Furthermore, the two submersed plants, E. canadensis and P. natans, were used in climate chamber experiments to study the fate of the metals in the plant–water system.
Emergent and terrestrial plant species accumulated high concentrations of metals in their roots under natural conditions but much less so in their shoots, and the accumulation increased further with increased external concentration. The submersed and free-floating species accumulated high levels of metals in both their roots and shoots. Metals accumulated in the shoots of E. canadensis and P. natans derived mostly from direct metal uptake from the water column.
The accumulation of Zn, Cu, Cd, and Pb in submersed species was in general high, the highest concentrations being measured in the roots, followed by the leaves and stems, E. canadensis having higher accumulation capacity than P. natans. In E. canadensis the Cd uptake was passive, and the accumulation in dead plants exceeded the of living with time. The capacity to quickly accumulate Cd in the apoplast decreased with successive treatments. Some of the Cd accumulated was readily available for leakage. In P. natans, the presence of mixtures of metal ions, common in stormwater, did not alter the accumulation of the individual metals compared to when presented separately. It is therefore, proposed that the site of uptake is specific for each metal ion. In addition cell wall-bound fraction increased with increasing external concentration. Further, decreasing the temperature from 20ºC to 5ºC and increasing the salinity from 0‰ to 5‰ S reduced Zn and Cd uptake by a factor of two.
In P. natans the metals were not translocated within the plant, while in E. canadensis Cd moved between roots and shoots. Thus, E. canadensis as opposed to P. natans may increase the dispersion of metals from sediment via acropetal translocation. The low basipetal translocation implies that neither E. canadensis nor P. natans will directly mediate the immobilisation of metal to the sediment via translocation.
To conclude, emergent and terrestrial plant species seem to enhance metal stabilization in the soil/sediment. The submersed plants, when present, slightly increase the retention of metals via shoot accumulation.
13
Fleta, Soriano Eva. "Mecanismos de protección frente al déficit hídrico reiterado en plantas." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/404785.
Full textAbstract:
En esta tesis doctoral se estudian los mecanismos que las plantas pueden disponer para hacer frente al déficit hídrico reiterado, ya que en la naturaleza los ciclos repetidos de estrés son mucho más frecuentes que un solo periodo de estrés.
La sequía es uno de los estreses ambientales que más afectan al crecimiento y desarrollo de las plantas, siendo el estrés abiótico el que más limita la producción de los cultivos. Además según los modelos climáticos actuales, la sequía va a seguir incrementando.
Para resistir estos ciclos de estrés las plantas disponen de mecanismos que les ayudan a hacer frente a las consecuencias de la sequía, como son el incremento de ácido abscísico, la fotoprotección y protección antioxidante, y la memoria.
La memoria es la capacidad de las plantas de responder mejor frente a un estrés tras haber estado previamente expuestas a dicho estrés. La memoria se puede dar tanto a nivel morfológico/estructural (como se aprecia en la reducción del tamaño de la antena de los cloroplastos indicado por la relación clorofila a/b), como a nivel bioquímico como se puede apreciar en los niveles de ácido abscísico. Plantas de Aptenia cordifolia previamente expuestas a la sequía mostraron mayores niveles de ácido abscísico y un tamaño menor de la antena del fotosistema II que las plantas expuestas a sequía por primera vez. La reducción en el tamaño de la antena también se observó en Silene dioica. El incremento en los niveles de ácido abscísico permite reducir la transpiración e inducir la síntesis de moléculas osmoprotectoras, y la reducción en el tamaño de la antena permite reducir la luz recibida por los fotosistemas, ya que el déficit hídrico suele darse en condiciones de exceso de luz cuando este sucede simultáneamente a un aumento en las temperaturas y la radiación solar, algo habitual en climas mediterráneos.
A pesar de los mecanismos de disipación del exceso de la energía en los cloroplastos, como el ciclo de las xantofilas, es inevitable que en momentos de estrés se incremente la producción de especies reactivas de oxigeno (ROS). Para hacer frente a estas moléculas, es decir para encargarse de la fotoprotección, las plantas disponen de antioxidantes como los tococromanoles o carotenoides que son los antioxidantes lipofílicos más abundantes en cloroplastos. Tras déficits hídricos reiterados, en plantas de maíz se observó un incremento del 65% en los niveles de plastocromanol-8 (PC-8), un tococromanol del que aún no se conocía si aumentaba en condiciones de sequía, siendo además su cantidad el 25% de los tococromanoles totales. Sugiriendo estos resultados que el primer estrés ayudó a prevenir el daño en el fotosistema II con un incremento en la cantidad de tococromanoles, como indica la mejora de Fv/Fm en las plantas en el segundo estrés pese a tener un menor contenido hídrico relativo.
Por último se estudió si la melatonina, una molécula con propiedades antioxidantes y reguladoras del crecimiento y desarrollo, ejercía un papel protector frente al déficit hídrico reiterado en plantas de maíz, y si actuaba como regulador o como hormona. Los resultados sugirieron que la melatonina endógena podría actuar como una hormona pero que aplicada exógenamente en el agua de riego en grandes cantidades podría ejercer un papel protector como antioxidante.
En conclusión, las plantas tienen diferentes mecanismos para aclimatarse a las nuevas condiciones como la memoria, la regulación hormonal, la protección antioxidante y la fotoprotección.Plant responses to reiterated drought differ from those to single drought exposure, and in nature plants are usually exposed to repeated cycles of drought. Plants have different mechanisms to withstand reiterated drought, as plant stress memory, antioxidants, photoprotection and phytohormones. Stress memory is the capacity of the organism to respond better to a given stress factor when individuals have already been challenged previously with the same stimulus, relative to those that have not been exposed to the stress before. Stress memory mechanisms were observed in the three species studied, Aptenia cordifolia, Silene dioica and Zea mays. In A. cordifolia, morphological adjustments were observed, as cahnges in the pigment composition leading to reductions of the light harvest complex (to increase photoprotection), as well as biochemical mechanisms, as the modulation of phytohomone contents (increases of abscisic acid). Apart of the reduction of the light harvest complex (also observed in S. dioica), lipophilic antioxidants such as tocochromanols and carotenoids have a role in photoprotection. In maize plants, an increase in tococromanols, including plastocromanol-8, was observed under reiterated drought, suggesting acclimation to prevent photoinhibitory damage, as indicated by the improvement of Fv/Fm despite lower relative water content in double-stressed plants. Also, it was studied if melatonin, an antioxidant and regulator, exerts a protective role against reiterated drought in maize. Results suggest that endogenous melatonin may have a protective role acting as a phytohormone, but applications of high amounts of melatonin may exert a protective role as an antioxidant. In conclusion, plants are able to acclimate to the new conditions (drought in this case) though various mechanisms, including memory, hormone regulation, antioxidant protection and photoprotection.
14
Wang, Yaodong. "Phytoremediation of mercury by terrestrial plants." Doctoral thesis, Stockholm : Department of Botany, Stockholm University, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-307.
Full text
15
Frigeri, Renita Betero Correa. "Relação entre raiz e parte aerea de plantulas de especies arboreas tropicais sob diferentes niveis de radiação solar." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/315143.
Full textAbstract:
Orientador: Ivany Ferraz Marques ValioTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
Made available in DSpace on 2018-08-10T07:14:10Z (GMT). No. of bitstreams: 1 Frigeri_RenitaBeteroCorrea_D.pdf: 1952747 bytes, checksum: 56334acb7a1f414b02ad8d99c78ee37c (MD5) Previous issue date: 2007
Resumo: O crescimento de plântulas de espécies arbóreas tropicais, em ambientes com disponibilidade luminosa contrastante, depende de interações entre características morfológicas e fisiológicas. Dentre as várias alterações morfológicas que ocorrem em condições de baixa irradiância, uma é a razão de crescimento entre a raiz e a parte aérea. A razão raiz:parte aérea de plântulas pode ser indicativa de especialização a diferentes ambientes. No geral, quanto mais sombreado o ambiente, maior a alocação de biomassa para as folhas. O aumento da biomassa da parte aérea (folhas e caules) se faz em detrimento da biomassa das raízes. Com o objetivo de verificar os efeitos de diferentes níveis de irradiância na alocação diferencial de fotossintatos, entre a parte aérea e subterrânea de plântulas de algumas espécies arbóreas tropicais, foram analisados o papel dos cotilédones e da região apical do caule e raiz na alocação, o teor de amido e a translocação de compostos de carbono. Plântulas de Copaifera langsdorfii, Dalbergia nigra, Hymenaea courbaril, Myroxylon peruiferum, Peltophorum dubium e Poecilanthe parviflora, consideradas tolerantes ao sombreamento e Bauhinia longifolia, Enterolobium contortisiliquum, Erythrina speciosa, Piptadenia gonoacantha, Senna macranthera e Schizolobium parahyba, consideradas pioneiras, foram crescidas por aproximadamente 2 meses sob 4, 18, 50 e 100 % da irradiância total. O acúmulo de biomassa de todas as espécies estudadas aumentou em resposta ao aumento da disponibilidade luminosa, bem como as taxas de crescimento relativo e a assimilação líquida. Verificou-se, em geral, redução na razão raiz: parte aérea das plântulas sob baixa irradiância. Apesar deste padrão geral, as espécies estudadas variaram quanto à razão raiz:parte aérea. Plântulas de espécies consideradas tolerantes ao sombreamento como Myroxylon peruiferum, Poecilanthe parviflora e Hymenaea courbaril apresentaram pouca alteração na razão raiz:parte aérea entre os diferentes tratamentos. Bauhinia longifolia, Copaifera langsdorfii, Erythrina speciosa, Enterolobium contortisiliquum e Piptadenia gonoacantha destacaram-se pelas altas razões raiz:parte aérea sob altas irradiâncias. A remoção dos cotilédones das plântulas, da maioria das espécies estudadas, resultou em redução da biomassa total. No geral, não houve diferença significativa na fração de biomassa alocada ao caule, às raízes e às folhas e na razão raiz:parte aérea, com a remoção dos cotilédones. O acúmulo relativo de amido nas folhas não pareceu associado ao decréscimo na partição de biomassa para as raízes, nas plântulas das espécies analisadas. Plântulas de Erythrina speciosa, que pouco diferiram neste aspecto quando mantidas a 2 e 50 % da irradiância, apresentaram a maior alteração na razão raiz:parte aérea. Plântulas de Poecilanthe parviflora, que não alteraram significativamente a distribuição de massa seca entre raiz e parte aérea, diferiram significativamente quanto ao acúmulo relativo de amido nas duas irradiâncias. Aparentemente, a remoção parcial dos diferentes órgãos contribuiu pouco para a redução da biomassa total. No geral, as plântulas das espécies analisadas revelaram um crescimento compensatório em resposta à remoção, tanto sob baixa quanto alta irradiância. A razão raiz:parte aérea não foi alterada em relação às plântulas intactas. A avaliação da distribuição de compostos com carbono radioativamente marcados demonstrou que a direção do movimento dos assimilados nas plântulas de Erythrina speciosa, Poecilanthe parviflora e Enterolobium contortisiliquum, após 48 horas de aplicação, deu-se no sentido da folha aplicada para o caule e em menor proporção para a raiz, exceto em plântulas de Hymenaea courbaril que retiveram quase a totalidade de assimilados na folha aplicada. No geral, não se observou uma diferença marcante em termos de movimento de assimilados, em plântulas mantidas a 2 e 50 % da irradiância. Em resumo, as espécies consideradas pioneiras apresentaram mudanças morfológicas e fisiológicas mais amplas, revelando grande plasticidade e habilidade em adaptar-se às variadas intensidades luminosas a que foram submetidas, em relação às espécies secundárias que revelaram baixa plasticidade fenotípica, a qual geralmente está associada à tolerância ao sombreamento. Entretanto, verificou-se a existência de espécies com respostas intermediárias e variáveis em relação aos parâmetros analisados
Abstract: The growth of seedlings of rain-forest tree species, in environments with contrasting light availability depends on the interaction between morphological and physiological characteristics. Among the various morphological alterations which occur in low-irradiance conditions, one of them is the ratio of growth between the root and shoot. The root: shoot ratio of seedlings can be suggestive to specialization to different environments. In general, the more shadowed the environment is, bigger is the biomass allocation on the leaves. The increase of biomass on the leaf area (leaves and stalk) occurs due to biomass detriment on the roots. Aiming to verify the different radiation level effects in the differential allocation of photosynthates between the root and the shoot of seedlings from some rain-forest tree species, the role of cotyledons and the apical region in the stalk and root in the allocation, the starch tenor and the translocation of carbon compounds radiolabelled. Seedlings of Copaifera langsdorfii, Dalbergia nigra, Hymenaea courbaril, Myroxylon peruiferum, Peltophorum dubium e Poecilanthe parviflora, considered shade tolerant and Bauhinia longifolia, Enterolobium contortisiliquum, Erythrina speciosa, Piptadenia gonoacantha,, Senna macranthera e Schizolobium parahyba, considered pioneers, were grown for approximately two months under 4, 18, 50 and 100 % of total irradiance. The biomass accumulation increased in all the studied species in response to light availability increase as well as the relative growth rate and net assimilation rate. In general, it was observed a reduction in the root:shoot ratio of seedlings under low irradiance. Despite this general pattern, the studied species varied regarding the root:shoot ratio. Seedlings of species considered shading tolerant as Myroxylon peruiferum, Poecilanthe parviflora e Hymenaea courbaril did not present a significant change in the root: shoot ratio. Bauhinia longifolia, Copaifera langsdorfii, Erythrina speciosa, Enterolobium contortisiliquum e Piptadenia gonoacantha contrasted due to high root: shoot ratio under high irradiance. The removal of cotyledons from the seedlings, in most of the studied species, resulted in reduction of the total biomass. Generally, there was not significant difference in the biomass portion allocated in the stalk, in the root and in the leaves and in the root:shoot ratio, with the removal of cotyledons. The accumulation of starch in the leaves did not seem associated to the decrease of biomass partitioning to the seedlings roots in the analyzed species. Seedlings of Erythrina speciosa which little differed in this aspect when put under 2 and 50% of irradiance, presented a higher alteration in the root: shoot ratio. Seedlings of Poecilanthe parviflora, which did not alter significantly the distribution of dry mass between root and shoot, differed significantly in the relative accumulate of starch in both irradiance. Apparently, the partial removal of these different organs little contributed for the total biomass reduction. In general, the analyzed seedling species, revealed compensatory growth in response to removal, either under low or high irradiance. The root:shoot ratio was not altered compared to the intact seedlings. The analyses of distribution of carbon compounds radioactively marked, showed that the moving direction of the assimilate in the seedlings of Erythrina speciosa, Poecilanthe parviflora e Enterolobium contortisiliquum, after 48 hours of application, occurred in the application leaf to stalk way also in lower portion to the root except in seedlings of Hymenaea courbaril which retained almost all the assimilate in the applied leaf. In an overall, a distinct difference was not observed in assimilates flow in seedlings put under 2 to 50 % of irradiance. Altogether, the species considered pioneers presented more ample morphological and physiological changes, revealing great plasticity and ability in adapting to various light intensities which they were submitted. In relation to the secondary species which revealed low phenotypical plasticity to which is generally associated with shadow tolerating therefore, there was found the existence of species with intermediate variable according to the analyzed parameters
Doutorado
Doutor em Biologia Vegetal
16
Sakamoto, Nelson Mamoru. "Sazonalidade, refrigeração e diferentes tipos de recobrimento na conservação pós-colheita de estacas de cordiline (Cordyline rubra Hügel)." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/11/11136/tde-02082005-123521/.
Full textAbstract:
O mercado mundial de floricultura gera um fluxo de quase US$ 7bilhões anuais, atualmente concentrado em países como Holanda, Alemanha, Itália, Colômbia, Costa Rica, Equador, Quênia, Tailândia, Malásia, Israel e EUA. O Brasil ainda contribui pouco, aproximadamente 0,3% do total, sendo a participação brasileira concentrada na exportação de mudas, bulbos, flores e folhagens tropicais. O Brasil possui grande potencial exportador de flores e plantas ornamentais através da organização dos produtores, profissionalização do setor, apoio governamental e desenvolvimento técnico. O emprego de técnicas simples de armazenamento poderia viabilizar o transporte por modais que não o aéreo, reduzindo custos e podendo prolongar a vida útil dos produtos, criando um diferencial de qualidade em relação aos concorrentes. Este trabalho compara cinco diferentes tipos de recobrimento em estacas de Cordyline rubra Hügel (película amilácea, pasta de parafina no ápice, pasta de parafina no ápice e vermiculita umedecida na base, saco plástico ou sem recobrimento), sazonalidade (estacas coletadas durante primavera ou outono), dois ambientes de armazenamento (ambiente refrigerado a 10ºC ou temperatura ambiente 22-32ºC) e diferentes períodos de armazenamento (30, 60, 90 ou 120 dias), a fim de reduzir sua atividade biológica, perda de água e ataque de patógenos. Foi escolhida esta espécie por ser muito apreciada como planta ornamental devido à beleza de suas folhas, e exportada na forma de estacas de diferentes tamanhos. O experimento foi conduzido nas dependências do Departamento de Produção Vegetal da Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, no município de Piracicaba, Estado de São Paulo. Foram utilizadas 615 estacas com 30 cm de comprimento por 3 cm de diâmetro. Um lote testemunha sem armazenamento de 15 estacas foi colocado em leito de enraizamento. Cada tratamento foi composto por 30 estacas pré-tratadas (tipos de recobrimento), submetidas a diferentes períodos de armazenamento (30, 60, 90 ou 120 dias), sendo divididos em 2 sub-tratamentos de 15 estacas (temperatura ambiente ou refrigerada), totalizando 120 estacas. Após o armazenamento foram cortados 3 cm da base de cada estaca, em seguida tratadas com IBA a 10.000 mg/L e colocadas em leito de enraizamento. Após 90 dias foram avaliados os seguintes parâmetros: porcentagem de desenvolvimento, número e massas de matéria fresca e seca de brotos, raízes e rizomas. Observou-se que as estacas colhidas na primavera apresentaram melhor enraizamento e produção de massas secas e frescas. Os menores períodos de armazenamento proporcionam melhor desenvolvimento das estacas, bem como estacas armazenadas em ambiente refrigerado apresentaram melhores resultados do que as mantidas em temperatura ambiente. Os tipos de recobrimento que melhor conservaram as estacas, em ordem decrescente de resultados, foram o saco plástico, parafina no ápice e vermiculita umedecida na base, parafina no ápice, película de amido e sem recobrimento. Conclui-se que o método mais prático foi embalar as estacas em sacos plásticos por não necessitar de fonte de calor para o preparo da película. Quanto maiores os períodos de armazenamento, menores desenvolvimentos de brotos, raízes e rizomas; os melhores resultados foram obtidos com estacas colhidas na primavera e armazenadas em ambiente refrigerado.The world market of floriculture, generates an annual flow of US$ 7billion, is currently based on countries like The Netherlands, Germany, Italy, Colombia, Costa Rica, Ecuador, Kenya, Thayland, Malaysia, Israel and the USA. The Brazilian contribution to the total world market is approximately 0.3%, where the mains exports are cuttings, bulbs, tropical fresh cut flowers and foliages. Brazil, however, has a great potential to increase its export of flowers and other ornamental plants through the better organization of producers, professionalization of the sector, government support and technical development. The use of simple storage techniques, would enable the transport through other means than airplanes, consequently reducing costs and adding extra shelf life to the product, creating a quality differentiation in relation to competitors. This work was aimed at comparing five types of coating of Cordyline rubra Hügel cuttings (starch film, paraffin paste at the apex, paraffin past at the apex associated with moist vermiculite at the base of the cuttings, plastic bags or no coating), seasonality (cuttings harvested during spring or autumn), two types of enviromental temperatures (refrigeration under 10ºC or environmental temperature between 22-32ºC) and different lengths of time on storage (30, 60, 90 or 120 days), in order to reduce their biologycal activity, water loss and pathogen attacks. This specie is very appreciated as an ornamental plant due to the beauty of their foliage and is exported as cuttings of different sizes. The experiment was carried out at the Departament of Plant Production at Luiz de Queiroz College of Agriculture, University of Sao Paulo, in Piracicaba City, Sao Paulo State, Brazil. A total of 615 cuttings were used, each measuring 30 cm by 3 cm diameter. A control group of 15 cuttings without storage was planted on rooting bed. Each treatment was comprised of 30 pre-coated cuttings (types of coating), stored at different periods (30.60, 90 or 120 days) and split into 2 sub-treatments of 15 cuttings, either stored at room temperature or under refrigeration, summing up 120 cuttings. After storage, each cutting had 3 cm excised from its base, prior to being treated with IBA 10.000 mg/L and placed at rooting beds. After 90 days, the following parameters were assessed: percentage of cuttings showing growth and development, number and fresh and dry matter of the shoots, roots and rhizoms. It was observed that cuttings obtained during the spring, showed better rooting and production of biomass. The shorter the storage periods the better the cutting sprouting. Cuttings stored under refrigeration showed better results than kept under room temperature. The types of coatings which best supported the longevity of the cuttings, in decrease order, were: plastic bag, paraffin paste at the apex and moist vermiculite at the base, paraffin on the apex, starch film and no coating. Such results allow to conclude that the most practical coating technique was found to be the use of plastic bags, which did not need heating for the prepare of the film. The longer the storage time the smallest the number of viable cuttings; best results where observed for cuttings harvested during the spring and kept under refrigeration storage.
17
Le, Fevre Ruth Elizabeth. "Phytate and plant stress responses." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708218.
Full text
18
Carneiro, Andrea Almeida. "Analyses of curcurbit P-protein promoters in transgenic plants." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/298810.
Full textAbstract:
P-proteins are structurally distinct proteins present in the sieve element-companion cell complexes of phloem tissue. Genomic clones encoding the two major P-proteins, the phloem filament protein (PP1) and the phloem lectin (PP2), were isolated and characterized. To understand mechanisms that control phloem-specific expression of these two genes, approximately 1 kb of the 5' flanking region from PP1 and PP2 genomic clones were fused with the GUS reporter gene and introduced into tobacco plants using Agrobacterium tumefaciens-mediated gene transfer. For both promoters, histochemical staining detected GUS activity specifically in the phloem tissue that was most easily detected in stems followed by midrib, secondary veins, roots, and leaf lamina of transgenic tobacco plants. GUS activity directed by the PP2 promoter was approximately 23 times greater than GUS activity directed by the PPI promoter. A nested set of 5' deletions between nucleotides -1014 and +32 were constructed to localize cis-elements that specify the patterns of PP2 gene expression in the phloem. Deletions within this region revealed that nucleotides -228 to +32 relative to the transcription initiation site contained sufficient information to direct phloem-specific gene expression, while positive regulators of promoter activity appeared to be located upstream of nucleotide -621. Mutation of a conserved 13-bp sequence, TTAAAAGAAGATA, found in the minimal PP2 promoter did not affect reporter gene expression. Sucrose responsive elements were identified in the PP2 promoter that could contribute to increased promoter activity in response to sugar. Finally we initiated studies to construct a phloem-specific promoter that could be induced by wound released compounds such as ethylene. Although not conclusive, our results suggest that it is possible to enhance phloem-specific expression in response to ethylene.
19
Köry, Jakub. "Multiscale modelling of nutrient and water uptake by plants." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/50425/.
Full textAbstract:
Growing populations in combination with the effects of climate change make the task of ensuring global food security in the future challenging. Water and various nutrients contained in soils are essential for the growth and survival of crop plants. Processes governing the dynamics of these substances are often highly complex and occur at various spatial scales. Because of that, and also due to limited possibilities for direct studies of soil processes in general, the ability to model such processes across these scales will most likely be crucial to address the food security challenge. Therefore, in this thesis, we model water and nutrient uptake by plant roots at various spatial scales. As all our models will be simulated numerically, we first test whether the software used throughout this thesis (FEniCS) gives us reliable numerical results (Chapter 2). We then proceed with the central part of this thesis, where we study nutrient uptake by root hairs using the method of homogenisation (introduced in Section 1.4.4). In Chapter 3, we first rederive the homogenisation result from [80] using a framework of periodic arrays of uptaking cylinders (hairs). Noticing that this framework can also be used to model nutrient or water uptake by a field of crops, we further study how well the homogenisation result compares with full-geometry numerics using various continuity equations and boundary conditions. In Chapter 4, we study the case where the radius of the root hair is much smaller than the inter-hair distance, which eventually leads us to a distinguished limit. In Chapter 5, we first establish that the framework from Chapters 3 and 4 is a suitable geometry for modelling nutrient uptake by root hairs, if the hair length is much smaller than the root radius. However, this is rarely the case. Therefore, we then investigate the effects of root surface curvature and hair length on the homogenised equation, and obtain a better approximation for the case where the hair length is comparable to the root radius. In the final two chapters, we introduce different complex problems relating to uptake by plants, and show how even simple multiscale techniques can provide us with useful insights into these problems. In Chapter 6, we show how to upscale nitrate uptake kinetics from a single transporter level to a root segment level, and then propose a model for nitrate uptake via low and high affinity transporters (see Section 6.1.2). Model predictions for the time of depletion, and a threshold nitrate concentration at which uptake ceases, are both in accordance with empirical values (Section 6.3.6). Finally, we demonstrate that under certain conditions, three-dimensional descriptions of the root system architecture are not necessary to estimate overall water and nitrate uptake, and that simple one-dimensional models can be used instead (Chapter 7).
20
Persson, Jörgen. "Organic nitrogen uptake by boreal forest plants /." Umeå : Dept. of Forest Genetics and Plant Physiology, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/s265-ab.html.
Full text
21
Waters, Mark T. "Plastid tubules in higher plants : an analysis of form and function." Thesis, University of Nottingham, 2004. http://eprints.nottingham.ac.uk/28928/.
Full textAbstract:
Besides photosynthesis, plastids are responsible for starch storage, fatty acid biosynthesis and nitrate metabolism. Our understanding of plastids can be improved with observation by microscopy, but this has been hampered by the invisibility of many plastid types. By targeting green fluorescent protein (GFP) to the plastid in transgenic plants, the visualisation of plastids has become routinely possible. Using GFP, motile, tubular protrusions can be observed to emanate from the plastid envelope into the surrounding cytoplasm. These structures, called stromules, vary considerably in frequency and length between different plastid types, but their function is poorly understood. During tomato fruit ripening, chloroplasts in the pericarp cells differentiate into chromoplasts. As chlorophyll degrades and carotenoids accumulate, plastid and stromule morphology change dramatically. Stromules become significantly more abundant upon chromoplast differentiation, but only in one cell type where plastids are large and sparsely distributed within the cell. Ectopic chloroplast components inhibit stromule formation, whereas preventing chloroplast development leads to increased numbers of stromules. Together, these findings imply that stromule function is closely related to the differentiation status, and thus role, of the plastid in question. In tobacco seedlings, stromules in hypocotyl epidermal cells become longer as plastids become more widely distributed within the cell, implying a plastid density-dependent regulation of stromules. Co-expression of fluorescent proteins targeted to plastids, mitochondria and peroxisomes revealed a close spatio-temporal relationship between stromules and other organelles. Stromule and plastid fusion could not be induced under conditions which promote substantial fusion of mitochondria. Data are presented suggesting that organelles may be able to pass between cells, and an experiment was designed to test this possibility in the C4 photosynthetic cells of maize. Inhibitor studies have shown that stromule and plastid movement is dependent on the actin cytoskeleton and the ATPase activity of myosin. An Arabidopsis gene, CHUP1, is responsible for chloroplast relocation in response to light intensity and encodes a chloroplast-localised actin-binding protein. To assess whether this protein is involved in stromule movement, CHUP1 was down-regulated with RNAi. Whilst plants with reduced CHUP1 expression exhibited a chup1 mutant phenotype, no significant effect on stromules was discovered. It was thus concluded that chloroplast relocation and stromule formation are two independent processes that employ different actin-dependent mechanisms. It is proposed that stromules act primarily to increase the plastid surface area in response to a number of developmental and environmental factors.
22
Vadapalli, Vatsala. "Role of N-Acylethanolamines in Plant Defense Responses: Modulation by Pathogens and Commercial Antimicrobial Stressors." Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc30521/.
Full textAbstract:
N-acyl ethanolamines (NAEs) are a class of lipids recently recognized as signaling molecules which are controlled, in part, by their degradation by fatty acid amide hydrolase (FAAH). On the basis of previous studies indicating increased NAE levels in a tobacco cell suspension-xylanase elicitor exposure system and the availability of FAAH mutants, overexpressor and knockout (OE and KO) genotypes in Arabidopsis thaliana, further roles of NAEs in A. thaliana plant defense was investigated. The commonly occurring urban antimicrobial contaminant triclosan (TCS) has been shown to suppress lipid signaling associated with plant defense responses. Thus, a second objective of this study was to determine if TCS exposure specifically interferes with NAE levels. No changes in steady state NAE profiles in A. thaliana-Pseudomonas syringae pv. syringae and A. thaliana-flagellin (bacterial peptide, flg22) challenge systems were seen despite evidence that defense responses were activated in these systems. There was a significant drop in enoyl-ACP reductase (ENR) enzyme activity, which catalyzes the last step in the fatty acid biosynthesis pathway in plants, on exposure of the seedlings to TCS at 10 ppm for 24 h and decreased reactive oxygen species (ROS) production due to flg22 in long term exposure of 0.1 ppm and short term exposure of 5 ppm. However, these responses were not accompanied by significant changes in steady state NAE profiles.
23
Planas, Portell Joan. "Metabolisme de poliamines en Arabidopsis i implicació en la resposta a l’estrès." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/120071.
Full textAbstract:
Les poliamines més comunes són putrescina, espermidina i espermina. En vegetals, els nivells d’aquests compostos incrementen en resposta a diferents tipus d'estrès ambiental. Tanmateix, es desconeix el significat fisiològic d’aquest augment. En general, s'ha atribuït un paper protector a espermidina i espermina, mentre que, en molts casos, la putrescina es considera només com a precursor de les altres dues poliamines. En la planta model Arabidopsis thaliana la putrescina es forma per descarboxilació d’arginina, mediada per arginina descarboxilas (ADC), que es codificada per dos gens: ADC1 i ADC2. En la present Tesis Doctoral, s’ha estudiat la resposta a l’estrès per fred i per sequera de plantes transgèniques d’Arabidopsis sobreexpressores dels gen homòlegs ADC1 i ADC2. Aquestes plantes tenen augmentats els nivells de putrescina, però no els d’espermidina ni d’espermina. Els resultats obtinguts mostren que les plantes que acumulen Put, per sobreexpressió d’ADC1 o ADC2, són més resistents a fred, sobretot si es tracta de plantes aclimatades prèviament. D’altra banda, la tolerància a deshidratació només s’ha observat en aquelles plantes que acumulen grans quantitats de Put via ADC2, i el grau de tolerància es proporcional als nivells de putrescina. Les plantes sobreexpresores d’ADC2 mostren una reducció en la taxa de transpiració i en la conductància estomàtica, i son més sensibles a ABA, encara que no s’han trobat diferencies en els nivells d’aquesta a l’hormona. Aquests resultats suggereixen que un dels mecanismes implicats en la resistència a sequera d’aquestes plantes, és la reducció de la pèrdua d’aigua per transpiració com a resultat d’una menor obertura estomàtica induïda per un augment en la resposta a ABA. Les diferencies entre els plantes sobreexpresores d’ADC1 i ADC2 podrien venir donades per una diferent localització de les corresponents proteïnes, ja que s’ha observat que ADC1 es troba al nucli, mentre que ADC2 es localitza als cloroplasts.
En conjunt els resultats obtinguts demostren que la putrescina te un paper intrínsec en la resposta de les plantes a estrès.
Els nivells de poliamines estan regulats també pel catabolisme. Les poliamines són degradades per desaminació oxidativa mediada per aminoxidases, que poden ser dependents de FAD (PAOs) o de coure (CuAOs). Clàssicament s’ha considerat que les amino oxidases tenen una localització apoplàstica. En Arabidopsis s’han descrit cinc isoformes de PAOs , tres s’han localitzat en peroxisomes, i les altres dues tenen una predicció de localització citoplasmàtica. Cap d’aquestes proteïnes du a terme l’oxidació terminal de PAs, si no que catalitzen una ruta de retroconversió, produint espermidina a partir d’espermina, i putrescina a partir d’espermina. Tot això fa pensar en com s’oxiden les PAs en l’apoplast d’Arabidopsis i si en els peroxisomes s’hi du a terme l’oxidació terminal. A. thaliana té 10 gens descrits com a CuAOs, però fins al moment només un (ATAO1) s’ha caracteritzat a nivell funcional. En aquesta tesis s’han caracteritzat a nivell funcional tres CuAOs d’Arabidopsis (AtCuAO1-3) que catalitzen l’oxidació terminal de l’espermidina i la putrescina. AtCuAO1, com l’ATAO1, és una proteïna extracel•lular, el que suggereix que el catabolismes de les PAs en l’apoplast d’Arabidopsis és mediat per CuAOs. AtCuAO2 i AtCuAO3 es troben en els peroxisomes, el que indica que el catabolisme terminal i la retroconversió funcionen de manera coordinada per mantenir la homeòstasi de poliamines, ja que l’acumulació de Put inhibeix les PAOs. El perfil d’expressió de les tres AtCuAOs en resposta a diferents estímuls exteriors suggereix una especificació funcional d’aquestes proteïnes enfront diferents tipus d’estrès. En aquesta tesis doctoral s’aporten, per primera vegada, evidencies sobre la integració de les dos rutes de oxidació de les poliamines que fins ara s’havien estudiat de manera independent.In plants, polyamine (putrescine, spermidine, spermine) levels increase in response to different abiotic stresses, but the biological meaning of this increase remains unclear. A protective role has been attributed to spermidine and spermine, while, in most cases, putrescine is considered only as a precursor of the other polyamines. In Arabidopsis, ADC (Arginine decarboxylase), the first enzyme involved in polyamine biosynthesis is encoded by two genes (ADC1 and ADC2).In this work, we have undertaken a genetic approach to study the effect of ADC1 and ADC2 over-expression in Arabidopsis freezing and drought tolerance. The obtained transgenic lines contain high putrescine levels and no increase in spermidine and spermine. Accumulation of putrescine by ADC1 or ADC2 over-expression is sufficient to promote freezing tolerance, mainly in cold-acclimated plants. Hower, only lines that accumulate Put by ADC2 over-expression are drought tolerant, and the degree of resistance correlates with Put content.This phenotype is related with a reduction in transpiration rate and stomata conductance, as well as an increased ABA-sensitivity. The differences between ADC1 and ADC2 over-expressing plants can be due to a different protein cellular localization. Polyamine levels are also regulated by degradation, mediated by FAD- and copper-dependent amine oxidases (PAOs and CuAOs). In Arabidospsis, five PAO isoforms, which oxidize polyamines by a back-conversion pathway, producing spermine and spermidine from putrescine have been characterized. However, only one of the ten gens annotated as CuAOs has been characterized so far. In this work, three CuAOs (AtCuAO1-3), involved in the terminal polyamine catabolism in Arabidopsis, have been functionally characterized. The results indicate a differential localization of AtCuAOs in the apoplast and peroxisomes together with a possible functional specification of AtCuAOs against different types of stress. Importantly, our results show that back-conversion and terminal catabolism work co-ordinately in peroxisomes to maintain polyamine homeostasis. For the first time we provide evidences for the integration of oxidative polyamine pathways that have so far studied in isolation.
24
Collins, R. P. "The role of calcium and potassium in salinity tolerance in Brassica rapa L. cv. RCBr seed." Thesis, Coventry University, 2012. http://curve.coventry.ac.uk/open/items/e0d653ff-7d6b-4827-9467-dc8bcb6ff621/1.
Full textAbstract:
The possibility of manipulating calcium (Ca2+) and potassium (K+) levels in seeds of Brassica rapa by altering parent plant nutrition and investigating the potential for increased salinity tolerance during germination, given that considerable amounts of literature imply that greater amounts of available exogenous Ca2+ and K+ can ameliorate the effects of salinity on both whole plant growth and germination, was evaluated. The investigation consisted of four growth trials. Two preliminary growth trials suggested that seed ion manipulation was possible without affecting the overall growth and vigour of the plant. After developing suitable high and low Ca2+ and K+ nutrient solutions for growth, a trial was carried out in a growth room and greenhouse, with various substrates and the seed of a certain size category was collected for subsequent ion and salinity tolerance analysis. Seed Ca2+ and K+ was significantly affected by growth substrate and nutrient solution and data showed that a significant negative regression relationship existed between seed Ca2+, K+ and Ca2+ + K+ levels and salinity tolerance. Further experimentation using hydroponic culture attempted to remove any possible effects of substrate and also to compare size categories of seed with a view to elucidating localisation of Ca2+ and K+. Seed Ca2+ was found to be significantly altered by nutrient solution in the two different sizes tested and higher Ca2+ nutrient solution was found to increase salinity tolerance in daughter seed. One significant negative regression correlation between salinity tolerance and seed K+ concentration existed in smaller seed, but disregarding seed size in a regression analysis of seed ion content and salinity tolerance, a significant negative relationship existed between seed Ca2+, K+ and Ca2++ K+. The results, especially in terms of Ca2+ nutrition, contradict much previous research that suggests increased salinity tolerance at germination can arise with the increased presence of Ca2+ and/or K+. Salinity tolerance was greater in seeds of larger size across all nutritional treatments and the smaller size range exhibited increased Ca2+ and K+ per μg seed. Ca2+ concentration in smaller seeds with greater surface area:volume ratios provided a clue to the potential localisation of Ca2+. Cross sectional staining showed that a greater proportion of seed Ca2+ may reside in the coat. This was confirmed by analysis which showed an approximate 50% split of total extractable seed Ca2+, regardless of size, between coat and embryo within a seed; the majority of which, per μg, resides in the coat. Further work looked at the relative solubility of the Ca2+ and K+ in these tissues and whole seed to look at the potential bioavailability of Ca2+ during germination from various parts of the seed. Most water soluble Ca2+ exists in the embryo and most insoluble Ca2+ exists in the coat, but coat Ca2+ was found to be ionically exchangeable and therefore bioavailable. K+ appeared mostly water soluble in embryo and coat. In line with previous whole plant research in this species, most Ca2+ is readily water soluble or ionically exchangeable in form and the possible negative effects of how increasing bioavailable Ca2+ may reduce salinity tolerance was discussed.
25
Gribble, Karleen Dawn. "Towards an understanding of the physiological abnormality of tissue cultured plants known as vitrification /." [Richmond, N.S.W.] : Horticulture, University of Western Sydney, Hawkesbury, 1999. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030513.144109/index.html.
Full textAbstract:
Thesis (Ph.D.) -- University of Western Sydney, Hawkesbury, 1999.Thesis submitted for the degree of Doctor of Philosophy. Spine title: Towards an understanding of vitrification in tissue cultured plants. Includes bibliographical references (leaves 175-203).
26
Titus, Charlene H. A. (Charlene Helecyn Agatha). "Sucrose transporters and sucrose uptake mechanisms in sugarcane." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16448.
Full textAbstract:
Thesis (MSc)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: The process of sugar accumulation and transport in sugarcane is still poorly understood. Understanding the processes involved in sucrose transport are important, since membrane transport might be important control points in this pathway. The goals of this project were to unravel the mechanisms of sugar transport in sugarcane culm tissue by using 14C-sugar analysis as well as molecular techniques to identify possible sucrose transporters. Developing (internode 2 and 4) and maturing (internode 8 and 15) culm tissue of sugarcane (Saccharum hybrid) commercial variety N19 was used for all tissue disc experiments. Tissue discs from internodes of different developmental stages were cut from field grown sugarcane plants (cv. N19) and the uptake of 14C-labelled glucose, fructose and sucrose measured. The uptake rates were measured at varying pH, temperature and concentrations of sugars. Hexoses were found to be the major sugar taken up and sucrose was only important when little hexose was available, as was found in the mature ripe internodes. Sucrose uptake differs between tissues and our study showed that sucrose was taken up rapidly at pH 5, similar to the pH optimum of most sucrose transporters Inhibition studies with TRIS (2-amino-2- (hydroxymethyl)-1,3-propanediol) and PCMBS (p-chloromercuribenzenesulphonic acid) indicated that more than one sucrose transporter activity may be present in the sugarcane system at different sucrose concentrations. To date work on sugarcane sucrose transporter expression on DNA and RNA level has been limited. Only recently a sucrose transporter from Saccharum hybrid sugarcane stem cDNA libray, ShSUT1 (Saccharum hybrid Sucrose Transporter ) was isolated and functionally characterized in the yeast strain SEY 6210 (Rae et al., 2004). In an effort to understand sucrose transport in sugarcane culm tissue, a partial sucrose transporter cDNA, ScSUT1(p) from Saccharum hybrid sugarcane a bud cDNA library was isolated, and cloned from a bud cDNA library. The clone was designated ScSUT(p) as a partial Sugarcane Sucrose Transporter. The ScSUT1(p) sequence showed 94% identity to ShSUT1 on nucleotide level over 1258 nucleotides and had an estimated open reading frame of 419 amino acids. Southern blot analysis indicated that the transporter had a low copy number and the ScSUT1(p) transcript expression was constitutive in sucrose accumulating and sucrose storing stem tissue, but was less abundant in immature tissue such as internodes 2 and 3 and in lateral buds. It was concluded that the primary function of ScSUT1(p), was not phloem unloading but that the transporter may be involved in phloem loading, as it is abundant in mature source leaves. ShSUT1 cDNA was obtained from Dr C Grof and the functionality of ShSUT1 as a sucrose transporter in Xenopus leavis oocytes was confirmed. However, electrophysiological measurements on the oocytes demonstrated no measurable current associated with sucrose challenge to the oocytes indicating that the transporter activity was either very low or possibly non-electrogenic. Further investigation is required to characterise the specific mechanism and kinetic properties of this transporter.
AFRIKAANSE OPSOMMING: Die proses van suikerakkumulering en -vervoer in suikerriet word steeds baie vaag verstaan. ‘n Deeglike begrip van die prosessewat betrokke is in die vervoer van sukrose is baie belangrik omdat transmembraan vervoer moontlik een van die belangrike beheerpunte in metabolisme mag wees. Die doelwitte van die studie was om ‘n beter begrip te bekom van die meganisme wat betrokke is by die vervoer en berging van sukrose in suikerriet. Die projek is in ‘n fisiologiese en ‘n molekulêre afdeling verdeel. In die fisiologiese afdeling is stingelweefsel van ‘n Saccharum hybried (variëteit N19) van verskillende stadiums van ontwikkeling (internodes 2-4, internode 8 en internode 15) gebruik. Opname van radioaktiewe (14C) sukrose, glukose en fruktose is as analise metode gebruik vir die suikeropname eksperimente. Die invloed van pH, suiker konsentrasie en inhibitore soos PCMBS (pchloromercuriphenylsulfonic acid) en TRIS (2-amino-2-(hydroxymethyl)-1,3-propanediol) op die tempo van suikeropname is ondersoek. Die molekulêre deel fokus hoofsaaklik op die identifisering, isolering en karakterisering van nuwe sukrose vervoerproteine in suikerriet, met behulp van PCR en heteroloë uitdrukking in Xenopus laevis oösiete. Die 14C - opname eksperimente het tot die volgende gevolgtrekkings gelei: Heksoses speel die belangrikste rol in die vervoer van suiker in die riet as daar min of geen sukrose teenwoordig is nie. Sodra daar sukrose in groot mate teenwoordig is soos in die geval van ontwikkelde, ryp internodes, is die rol van sukrose egter belangriker. Sukrose is die maklikste opgeneem by pH 5, wat naby die pH optimum van die meeste sukrose vervoerproteïene is. TRIS en PCMBS het beide ‘n inhiberende effek op sukrose opname gehad, maar die invloed was groter by die laer sukrose konsentrasies. Tot onlangs was daar baie min inligting oor sukrose vervoer in suikerriet op DNA en RNA vlak. Die eerste sukrose vervoerprotein uit suikerriet, ShSUT1 (Saccharum Hibried Sukrose Transporter) is eers onlangs uit ‘n stingel - cDNA biblioteek geïsoleer (Rae et al., 2004) en die funksionering daarvan is in ‘n gisras (SEY6210) getoets. In my pogings om sukrose vervoer te verstaan is ‘n gedeeltelike cDNA, naamlik ScSUT(p) (partial Sugarcane Sucrose Transporter) van 1258 nukleotiede, uit cDNA afkomstig van suikerrietbotsel geïsoleer. Die nukleotiedvolgorde stem 94% ooreen met ShSUT1 en kodeer vir ‘n moontlike oopleesraam van 419 aminosure. Southern analises het aangedui dat ScSUT(p) ‘n lae kopie getal het, in ooreenstemming met wat vir ander sukrose vervoerproteïene gevind is. Northern analises het getoon dat die uitdrukking van ScSUT(p) konstitutatief is in sukrose akkumulerende sowel as sukrose bergingsweefsel. Jong weefsel (internode 2 en 3) het baie lae uitdrukking getoon, met die hoogste uitdrukking in blaarweefsel. Uit die resultate is afgelei dat ScSUT(p) ‘n rol in floeëmlading en -ontlading mag speel. Xenopus laevis oösiete, is as ‘n heteroloë uitdrukking sisteem gebruik om te bevestig dat ShSUT1 as ‘n sukrose vervoerproteïen funksioneer. Elektrofisiologie het nie daarin geslaag om ShSUT1 se spesifieke werkingsmeganisme te identifiseer nie. Aanduidings is egter gevind dat ShSUT1 moontlik nie as ‘n H+/sukrose simportsisteem werk nie, maar by gefasilliteerde vervoer van sukrose betrokke mag wees. Verdere navorsing is noodsaaklik om die meganisme van ShSUT1 se werking te verstaan.
27
Lundmark, Maria. "Low temperature acclimation in plants : alterations in photosynthetic carbon metabolism." Doctoral thesis, Umeå : Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1333.
Full text
28
Harris, Taahir. "Bambara groundnut (Vigna subterranean) from Mpumalanga province of South Africa: phytochemical and antimicrobial properties of seeds and product extracts." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2789.
Full textAbstract:
Thesis MTech (Food Technology))--Cape Peninsula University of Technology, 2017.Bambara groundnut (Vigna subterranea) an indigenous legume cultivated in Sub-Saharan Africa has been proclaimed to have medicinal properties from communities and in rural areas. However, there is not enough scientific information to validate these claims. Therefore, this study aimed to identify possible medicinal properties of Bambara groundnut (BGN), by analysing the phytochemical and antimicrobial properties of BGN seed and product extracts from Mpumalanga province within South Africa. The BGN extracts (70% methanol, 70% ethanol, milli-Q water) from seeds and products (milk and yoghurt) were screened for the presence of alkaloids, flavonoids, phenols, riboflavin and thiamine using analytical laboratory methods for basic screening, high-performance liquid chromatography (HPLC) and gas chromatography (GC) for quantification. The antimicrobial activity involved direct bioautography and minimum inhibitory concentration (MIC) against six antibiotic-resistant microorganisms, Acinetobacter baumannii ATCC 19606T, Enterococcus faecalis ATCC 29212, Klebsiella pneumoniae subsp. pneumoniae ATCC 700603, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus subsp. aureus ATCC 33591 and Candida albicans ATCC 24433. For the seed extracts, flavonoids and phenols were highly concentrated in the red and brown hulls of BGN compared to whole and dehulled BGN. Organic solvents in comparison to water yielded the highest concentration of flavonoids, whilst water yielded the highest concentration for phenols. Flavonoid compounds that were detected at the highest concentrations were rutin (24.458 ± 0.234 mg.g-1, brown hull extracted with 70% methanol), quercetin (0.070 ± 0.043 mg.g-1, red hull extracted with 70% methanol), kaempferol (0.391 ± 0.161 mg.g-1; brown hull extracted with 70% ethanol) and myricetin (1.800 ± 0.771 mg.g-1; red hull extracted with 70% methanol). For phenol compounds, gallic acid (0.009 ± 0.004 mg.g-1; brown hull extracted with milli-Q water), catechin (0.026 ± 0.041 mg.g-1; brown hull extracted with milli-Q water), methyl gallate (0.008 ± 0.013 mg.g-1; brown whole extracted with milli-Q water), chlorogenic acid (0.115 ± 0.199 mg.g-1; brown hull extracted with milli-Q water) and ellagic acid (0.105 ± 0.082 mg.g-1; red hull extracted with milli-Q water) were detected. Vitamins B1 and B2 (riboflavin and thiamine) were mostly present in milli-Q water extracts. Black-eye hull had the highest concentration of thiamine (vitamin B1) and riboflavin (vitamin B2) consisting of 0.072 mg.g-1 (extracted with milli-Q water) and 0.002 mg.g-1 (extracted with 70% ethanol and 70% methanol). Red and brown hull extracts from organic solvents (70% ethanol and 70% methanol) showed the highest antimicrobial activity, whereas the whole, dehulled and hulls (black-eye and brown-eye) extracts had no antimicrobial activity. As for BGN products extracts, flavonoid compounds that were detected at the highest concentrations were rutin (5.694 mg.g-1, whole BGN milk, milli-Q water), quercetin (0.703 mg.g-1, whole BGN yoghurt, milli-Q water) and myricetin (0.987 mg.g-1, whole BGN yoghurt, 70% ethanol).
29
Chow, Elaine Kiaw Fui 1972. "An investigation into the use of ROL genes to alter root formation and growth in transgenic plants." Monash University, Dept. of Biological Sciences, 2001. http://arrow.monash.edu.au/hdl/1959.1/9092.
Full text
30
Nahar, Maksuda Anjuman. "Regeneration of plants from anther, callus and protoplast cultures of rice (Oryza sativa L.)." Thesis, University of Nottingham, 1994. http://eprints.nottingham.ac.uk/13505/.
Full textAbstract:
The work described in this thesis focuses on the development of fully reproducible systems of plant regeneration through embryogenic callus and totipotent protoplast cultures of rice (Oryza sativa L. cv. Taipei 309). The calli originated from different explants, including excised anthers, isolated microspores, mature seed-embryos, immature seed-embryos and leaf-base meristems. In the callus culture and plant regeneration studies, excised anther-derived callus produced higher numbers of green (90.5%) and albino (9.5%) plants, both haploids (81.2%) and diploids (18.8%), compared to other explants. The plant regeneration frequency from mature seedembryo-derived callus varied with callus age and embryogenicity of the callus. A maximum of 20% plant regeneration was obtained with approx. 2% of the regenerated plants being albinos. In the case of mature or immature seed-embryos and leaf-base meristems, plant regeneration frequency from callus was dependent on some more specific factors, in addition to callus age and embryogenicity. These factors were the age of seedlings grown in vitro and the age of immature embryos after anthesis for leaf-base meristem and immature embryo cultures, and also the scutellar surface orientation of mature or immature embryos during callus culture initiation. The present study also focused on the plating efficiencies and plant regeneration frequencies obtained from culture of embryogenic cell suspension-derived protoplasts. These varied with the explant source, the embryogenic nature and age of the callus during suspension initiation, the age of the embryogenic suspension culture, the time of enzymatic digestion, the plating density, viability of protoplasts and use of the suspensions at their exponential (actively dividing) growth stage. The results from this study indicated that leaf-base meristem and anther calli-derived suspensions retain their regenerability for a longer time compared to suspensions derived from mature seedscutellum and immature seed-derived embryos. Maximum plant regeneration frequency (45%) was obtained from embryogenic suspensions derived from mature seedembryos. A detailed study of different agronomic characteristics of 57 protoclonal plants (mature seed-scutellum-derived) was performed and the statistical analysis of the data indicated a range of variability among the protoclonal plants and also between the protoclonal and seed-derived plants. A detailed study of the ploidy levels of regenerated plants obtained through different culture systems (callus and protoplasts) was performed by flow cytometry and chromosome counting of meristematic cells. The results showed that anther calliderived plants were mostly haploids, protoplast-derived plants of leaf-base meristem, anther, and mature seed-scutellum origin were mostly tetraploids and in between these two groups, diploids, triploids and aneuploids were also present.
31
Au, Kin Cheong Kenneth. "Mutational analysis of membrane traffic in Arabidopsis thaliana." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:e3e14949-f3ed-4a09-8475-5945e5c6b11c.
Full textAbstract:
To identify novel and essential components of the plant membrane trafficking mechanisms, Arabidopsis membrane trafficking mutants from fluorescent protein-based forward genetic screens were characterized. First, four novel glutathione synthase (GSH2) mutant alleles featured swollen endoplasmic reticulum (ER)-derived bodies that accumulated a soluble secretory marker. Consistent with the role of GSH2 in glutathione biosynthesis, the loss-of-function mutant alleles exhibited gamma-glutamylcysteine (γ-EC) hyperaccumulation and glutathione deficiency. The aberrant ER morphology was ascribed to the γ-EC accumulation. Redox-sensitive fluorescent protein revealed that gsh2 seedlings maintained a reduced cytoplasm at steady state but were more sensitive to oxidative challenge. Second, Mut 21 was a conditional mutant that accumulated a secretory marker in the alkalized apoplast at restrictive temperature (31˚C). The mutant was identified as carrying a mutant allele of tuftelin-interacting protein 11 (TFIP11), which has been implicated in regulating redifferentiation and cell proliferation through a cytokinin signalling pathway. Hence, it was postulated that the changes in response to cytokinin affect auxin-mediated acidification of the apoplast. Third, Mut 43 was a conditional mutant that accumulated a soluble secretory marker in the ER and unidentified punctate structures at restrictive temperature, and exhibited perturbations in ER export of a soluble protein marker. Moreover, the mutant showed severe growth defects and abnormal radial root swelling in the apical elongation zone. A mutation identification method through deep-sequencing of the wild-type siblings in outcrossed heterozygous mutant families was developed and tested in Mut 43. At the time when this thesis was prepared, bioinformatic analysis has assigned Mut 43 to the bottom arm of chromosome two and predicted a 300kb mapping interval based on the observed bias in single nucleotide polymorphism ratios. This work demonstrates the feasibility of using forward genetics to study plant-specific aspects of membrane trafficking mechanisms and incorporates new technology to streamline the process of gene identification.
32
Dias, Leonardo Lucas Carnevalli. "Aspectos fisiológicos, bioquímicos e análise proteômica comparativa durante a maturação, germinação e conversão em plantas de embriões de Ocotea catharinensis Mez. (Lauraceae)." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/87/87131/tde-10082009-172459/.
Full textAbstract:
A semelhança entre os eventos da embriogênese zigótica e somática permite que sejam estabelecidos parâmetros para o acompanhamento destes dois processos. Neste trabalho foi estudada a embriogênese somática em Ocotea catharinensis, nas fases de maturação e germinação, além do processo germinativo da semente zigótica, avaliando-se parâmetros bioquímicos, e a expressão diferencial de proteínas. O tratamento com ABA + PEG em culturas de embriões somáticos apresentou variações semelhantes a apresentadas por embriões zigóticos no estádio de maturação. Não se observou a germinação de embriões somáticos, contudo verificou-se que a desidratação prévia promoveu importantes alterações bioquímicas. Durante a germinação, não se observou à síntese de novas proteínas no embrião zigótico. Os estudos proteômicos no desenvolvimento da semente permitiram a seleção de polipeptídios, marcadores estádio-específicos. Os resultados obtidos possibilitam a otimização e melhor entendimento das etapas da embriogênese somática, em espécies com sementes recalcitrantes, como O. catharinensis.The great similarity among the events of zygotic and somatic embryogenesis allows the establishment of parameters for accompaniment of these processes. In the present work it was studied the somatic embryogenesis in Ocotea catharinensis, in the maturation and germination phases, and the zygotic embryogenesis. The biochemical parameters and differential expression of proteins were evaluated: The treatment with ABA + PEG presented similar variations for zygotic embryos in the maturation stage. The germination was not observed for somatic embryos; however, it was verified that the previous dehydration promoted important biochemical alterations. With relation to the zygotic embryo, throughout the germination process, the synthesis of new proteins was not observed. The proteomic studies carried out throughout seed development, allowed the selection of polypeptides with differential expression. The results obtained open perspectives for the methodology optimization of the somatic embryogenesis, for species with recalcitrant seeds, like O. catharinensis.
33
Thelander, Mattias. "Studies of molecular mechanisms integrating carbon metabolism and growth in plants /." Uppsala : Dept. of Plant Biology and Forest Genetics, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/a432.pdf.
Full text
34
Choudhury, Feroza Kaneez. "Rapid Metabolic Response of Plants Exposed to Light Stress." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1157543/.
Full textAbstract:
Environmental stress conditions can drastically affect plant growth and productivity. In contrast to soil moisture or salinity that can gradually change over a period of days or weeks, changes in light intensity or temperature can occur very rapidly, sometimes over the course of minutes or seconds. So, in our study we have taken an metabolomics approach to identify the rapid response of plants to light stress. In the first part we have focused on the ultrafast (0-90 sec) metabolic response of local tissues to light stress and in the second part we analyzed the metabolic response associated with rapid systemic signaling (0-12 min). Analysis of the rapid response of Arabidopsis to light stress has revealed 111 metabolites that significantly alter in their level during the first 90 sec of light stress exposure. We further show that the levels of free and total glutathione accumulate rapidly during light stress in Arabidopsis and that the accumulation of total glutathione during light stress is dependent on an increase in nitric oxide (NO) levels. We further suggest that the increase in precursors for glutathione biosynthesis could be linked to alterations in photorespiration, and that phosphoenolpyruvate could represent a major energy and carbon source for rapid metabolic responses. Taken together, our analysis could be used as an initial road map for the identification of different pathways that could be used to augment the rapid response of plants to abiotic stress. In addition, it highlights the important role of glutathione in initial stage of light stress response.
Light-induced rapid systemic signaling and systemic acquired acclimation (SAA) are thought to play an important role in the response of plants to different abiotic stresses. Although molecular and metabolic responses to light stress have been extensively studied in local leaves, and to a lesser degree in systemic leaves, very little is known about the metabolic responses that occur in the different tissues that connect the local to the systemic leaves. These could be important in defining the specificity of the systemic response as well as in supporting the propagation of different systemic signals, such as the reactive oxygen species (ROS) wave. Here we report that local application of light stress to one rosette leaf resulted in a metabolic response that encompassed local, systemic and transport tissues (tissues that connect the local and systemic tissues), demonstrating a high degree of physical and metabolic continuity between different tissues throughout the plant. We further show that the response of many of the systemically altered metabolites could be associated with the function of the ROS wave, and that the level of eight different metabolites is altered in a similar way in all tissues tested (local, systemic, and transport tissues). These compounds could define a core metabolic signature for light stress that propagates from the local to the systemic leaves. Taken together, our findings suggest that metabolic changes occurring in cells that connect the local and systemic tissues could play an important role in mediating rapid systemic signaling and systemic acquired acclimation to light stress.
35
Martyn, Amelia. "The physiology and control of bract browning in waratahs (Telopea spp.)." Faculty of Agriculture, Food and Natural Resources, 2005. http://hdl.handle.net/2123/5773.
Full textAbstract:
PhDThe waratah, Telopea speciosissma and its hybrids with other Telopea species, is an Australian native species grown for domestic and export cut flower markets. The showy floral bracts surrounding the inflorescence often suffer from bract browning, reducing the market value and export potential of the blooms. Prior to this project, the physiological cause of the disorder was not known, although bract browning had been attributed to water stress, heat stress, high light (particularly after frost), wind and mechanical damage. Bract browning was reportedly minimised when waratahs were grown in shaded conditions, although the reduction in browning by shade had not been quantified. The aim of this project was to examine the physiological cause of the bract browning disorder and investigate methods for control. The appearance, timing, and severity of the bract browning disorder was initially characterised by dissecting waratah buds from commercial growers throughout NSW. Bract browning became evident in the six to eight weeks prior to harvest, coinciding with rapid bract and flower expansion. A survey of commercial waratah growers, initiated by NSW Agriculture and the Waratah Industry Network and analysed by the author, corroborated these results. The survey showed that bract browning was observed in all years between 1999 and 2003, with relatively high severity (scores from three to five out of a possible five) in three of those years. Scores or counts of brown bracts were used to assess the severity of the disorder, the latter including the number of senesced floral bracts following browning as a measure of browning severity. The position and timing of browning suggest light damage or localised calcium deficiency could play a role in the development of browning. The bract browning disorder was studied in further experiments on potted red waratahs of cultivars ‘Fire and Brimstone’, ‘Olympic Flame’ and ‘Sunflare’ at the Mount Annan Botanic Garden; on commercially grown ‘Wirrimbirra White’ waratahs at Jervis Bay; and on natural populations in the Royal National Park. The effect of calcium nutrition on bract browning was studied at Mount Annan in 2001 and 2002, testing the hypothesis that browning may be caused by a localised calcium deficiency similar to lettuce tipburn or poinsettia bract necrosis. Waratah bracts had significantly less calcium in all fractions than leaves, with the procedure of Ferguson et al. (1980) used to separate physiologically active, oxalate associated and residual calcium. Calcium chloride sprays applied to developing bracts increased total bract calcium by about 25% in ‘Sunflare’ and ‘Olympic Flame’ cultivars, but not in ‘Fire and Brimstone’. However, application of calcium as a spray to the developing bracts, or as gypsum to the potting medium did not significantly reduce bract browning scores. These results and the development of bract browning in exposed, rather than enclosed tissue, suggest that factors other than calcium are involved in the development of bract browning. The light environment (full sun or 50% shade cloth) had a greater effect than irrigation frequency on bract browning of ‘Sunflare’ and ‘Olympic Flame’ waratahs in 2001. Waratahs grown under 50% shade cloth showed less bract browning at flower maturity than waratahs grown in full sun. This result was corroborated by subsequent experiments in 2002 and 2003. For example, in 2002, shade cloth reduced browning and bract loss by 30-60% at flower maturity, compared to waratahs grown in full sun. Shading waratahs from bud initiation in late summer (December-January) or bud opening in late winter (July-August) was equally effective in reducing browning. Shade cloth (50%) significantly reduced the light intensity experienced by waratah plants throughout the day, as well as reducing the daily maximum temperature and minimum relative humidity. Natural shade conditions at the Royal National Park effectively prevented browning of floral bracts, although the smaller basal bracts still turned brown and senesced. The development of bract browning as waratahs matured was linked to the development of chronic photoinhibition, measured as a decrease in predawn photosynthetic efficiency using chlorophyll fluorescence techniques. Waratah bracts were unable to maintain efficient photosynthesis in full sun conditions and reached saturation of non-photochemical quenching at lower light intensities than leaves. This suggests that bract tissue is adapted to a lower light environment than leaf tissue. Outer bracts had a significantly lower photosynthetic efficiency (Fv/Fm) than leaves early in flower development, as they were exposed to the environment for a prolonged period. Outer bracts also began to senesce towards flower maturity, particularly in full sun, increasing their susceptibility to damage. Inner waratah bracts were able to maintain a high photosynthetic efficiency prior to exposure, but photosynthetic efficiency decreased significantly at the intermediate stage of floral development, as inner bracts were no longer protected by outer bracts. Waratah leaves were more resilient than bracts, and did not suffer from chronic photoinhibition or browning during flower development. The increased susceptibility of bracts to photoinhibition and browning parallels results in other species, such as Dendrobium, where floral tissue experiences photoinhibition, bleaching and necrosis at lower light intensities than leaf tissue. Bracts on shaded waratahs maintained higher chlorophyll, carotenoid and anthocyanin concentrations than sun-exposed bracts, giving more intense flower colour and higher quality blooms. The significant decrease in bract pigmentation in the sun is likely to be a result of pigment destruction following photoinhibition, and has been noted in susceptible tissues of other species, such as Illicium (star anise) leaves. The presence of anthocyanins did not reduce bract browning in waratahs, with the concentration of UV-absorbing compounds showing a stronger positive correlation with protection from photoinhibition than the concentration of anthocyanins. However, anthocyanin concentrations were significantly lower in sun-exposed bracts, and brown compounds appeared to replace anthocyanins in the epidermal cells of brown bracts. Thus, it seems likely that browning in waratah bracts is the visible manifestation of oxidative damage to cell components, following chronic photoinhibition. Light-induced oxidative damage can lead to yellowing and pigment bleaching, lipid peroxidation, the development of necrotic lesions and senescence. However, lipid peroxidation as measured by the malionaldehyde assay gave no indication of oxidative damage to waratah bract tissue. This was probably due to the presence of anthocyanins and other flavonoids and sugars other than sucrose in bract tissue interfering with the colourimetric measurement of thiobarbituric acid reactive substances. The extensive planting of waratahs in NSW in the last five years suggests that the total value of lost production due to bract browning is likely to increase in the future. The browning disorder may also prevent the establishment of waratahs in other markets, as international cut-flower markets demand high quality blooms free from blemishes. The results of this study show that bract browning, photoinhibition and pigment loss are minimised by protecting waratahs from high light intensities from bud opening until harvest. However, the consequences of shading waratahs throughout the year require further investigation, as does the use of different percentages of shade cloth or other methods to reduce incident light.
36
Patto, Leonardo Silva. "Acrotonia da brotação de macieira em região de inverno ameno." Universidade Tecnológica Federal do Paraná, 2017. http://repositorio.utfpr.edu.br/jspui/handle/1/2287.
Full textAbstract:
CAPESDurante a dormência, as plantas de clima temperado cessam temporariamente o crescimento visível. No caso da macieira sabe-se que a temperatura é o fator ambiental que mais influencia a dormência. A planta necessita de baixas temperaturas para induzir a entrada e posteriormente a saída da dormência, para então retomar o crescimento vegetativo. Sabe-se que quando não ocorre acúmulo suficiente de frio, as plantas apresentam crescimento errático, com brotação ocorrendo predominantemente na porção distal dos ramos, comprometendo a brotação satisfatória. No entanto, há pouca informação sobre o metabolismo destes carboidratos e sua relação com a dormência de plantas em condições de inverno ameno. Contudo o objetivo deste trabalho foi avaliar as diferenças biológicas e bioquímicas entre as porções distal e proximal de ramos de macieira que influenciam a acrotonia. De abril a outubro dos anos de 2012, 2013 e 2014, foram coletados ramos e esporões de três cultivares de macieira (Eva, Galaxy e Fuji Suprema) cultivadas em um pomar comercial no município de Plamas-PR. Para avaliar a intensidade da dormência em gemas vegetativas foi realizado o teste de estacas de uma só gema, e o teste de Tabuenca para as gemas florais. Variáveis bioquímicas também foram avaliadas como o teor de proteínas solúveis; atividade de alfa-amilase; açúcares (glicose, frutose, sacarose e sorbitol); amido e umidade. De forma geral as cultivares apresentaram tempo médio de brotação (TMB) menores do que em clima temperado. A porcentagem de brotação manteve-se alta na maioria das coletas para as três cultivares. O teste de Tabuenca confirmou a precocidade da cultivar Eva e mostrou comportamento muito semelhante entre a ‘Galaxy’ e a ‘Fuji Suprema’. Além disso foi observado um intervalo muito curto entre a saída da endodormência em condições de forçagem e em condição de campo. A umidade ponderal variou conforme o padrão da temperatura em cada ano, sendo que em 2013, ano de maior acúmulo de frio a umidade ponderal apresentou os menores valores para todas as cultivares. Em 2013 a tendência de aumento da atividade da alfa-amilase e no teor de proteína coincidiram com o menor valor de TMB. A glicose e frutose apresentaram comportamento muito semelhantes entre si durante as observações. O teor de sacarose variou de ano para ano, não apresentando um padrão fixo. O sorbitol, açúcar mais abundante no xilema, tende a ser mais constante durante a dormência com leve tendência de redução próximo à brotação. O teor de amido tende a diminuir com os primeiros acúmulos de horas frio, no entanto frequentemente sofre ressíntese, devido às ondas de calor comuns no inverno. Existe diferenças entre as porções dital e proximal dos ramos para todas as variáveis analisadas, com teor de carboidrato, atividade enzimática, proteínas e umidade predominantemente maiores na porção distal dos ramos, com algumas exceções pontuais. Isso pode estar associado à ocorrência de acrotonia em macieiras. As plantas avaliadas parecem não entrar em dormência profunda em condição de inverno ameno, tendo seu metabolismo muito sujeito às oscilações de temperatura. O metabolismo das plantas tende a mudar de ano para ano de acordo com o padrão do inverno em cada ano.
During dormancy, temperate plants temporarily stops visible growth. In apple trees, it is known that temperature is the environmental factor that most influences dormancy. The plant requires low temperatures to induce input and then to output endodormancy, thus resumption vegetative grow. It is known that when there isn’t sufficient chilling accumulation, plants present erratic growth, with budbreak occurring predominantly in the distal portion of the branches, compromising the satisfactory budbreak. However, there is little information on the metabolism of these carbohydrates and their relationship to plant dormancy in subtropical humid climates. This work aimed to evaluate the biological and biochemical differences between the distal and proximal portions of apple tree branches that influence acrotonia. From April to October of 2012, 2013 and 2014, branches and spurs of three apple cultivars (Eva, Galaxy and Fuji Suprema) were harvested in a commercial orchard in Palmas-PR. In order to evaluate the dormancy intensity in vegetative and floral buds, single bud cuttings test and Tabuenca test were carried out, respectively. Biochemical variables were also evaluated such as soluble protein content; Alpha-amylase activity; Soluble sugars (glucose, fructose, sucrose and sorbitol); Starch and water content. In general, the cultivars showed the Mean Time to Budbrst (MTB) lower than in temperate climate. The budburst percentage remained high in most of the observation dates for the three cultivars. The Tabuenca test confirmed the precocity of the cultivar Eva and showed very similar behavior between 'Galaxy' and 'Fuji Suprema'. In addition, a very short interval between the endodormancy output under forcing conditions and in field condition was observed. The water content varied according to the temperature pattern in each year, and in 2013, the year of greatest cold accumulation, the lowest values for all cultivars were observed. In 2013, the trend of increased alpha-amylase activity and protein content coincided with the lower value of MTB. Glucose and fructose presented very similar behavior among themselves during the observations. The sucrose content varied from year to year and did not present a fixed pattern. Sorbitol, sugar most abundant in the xylem, tends to be more constant during dormancy with a slight reduction tendency close to budding. The starch content tends to decrease with the first chilling accumulations, however it often undergoes resynthesis due to the heat waves common in winter. There are differences between the distal and proximal portions of the branches for all variables analyzed, with carbohydrate content, enzymatic activity, proteins and humidity predominantly larger in the distal portion of the branches, with some occasional exceptions. This may be associated with the occurrence of acrotonia in apple trees. The evaluated apple trees do not appear to fall into deep endodormancy in a mild winter condition, their metabolism seems to be very subject to temperature oscillations. Plant metabolism tends to change from year to year according to the winter pattern in each year.
37
Gribble, Karleen D., of Western Sydney Hawkesbury University, and Faculty of Science and Technology. "Towards an understanding of the physiological abnormality of tissue cultured plants known as vitrification." THESIS_FST_HPS_Gribble_K.xml, 1999. http://handle.uws.edu.au:8081/1959.7/417.
Full textAbstract:
For this research, the abnormality of tissue cultured plantlets,vitrification, was examined in Gypsophila paniculata.Measurement of the relative water content and water saturation deficit of plantlets in culture revealed that vitrified plantlets contain relatively more water and less air spaces than non-vitrified plantlets.The effect of relative humidity on vitrification and growth was investigated using a variety of methods.From the results found, it was determined the defining characteristic of vitrified plantlets is water filled intercellular spaces. It was also determined that the primary cause of vitrification is high relative humidity resulting in a lack of transpiration in vitro but that other factors such as unbalanced mineral nutrition or high medium cytokinin can exacerbate vitrification.Further research in tissue culture may investigate the influence of relative humidity on plant growth and morphology, the mechanism by which plants exclude water from their intercellular spaces and refine in vitro tissue mineral analysis as a means by which critical mineral concentrations can be determined.Doctor of Philosophy (PhD)
38
LAIBI, SAMI RESHAK. "EFFECT OF ENVIRONMENTAL FACTORS AND APPLIED GROWTH REGULATORS ON GROWTH, CYTOKININ PRODUCTION AND PHYSIOLOGICAL CHANGES OF PEPPERS (CAPSICUM ANNUUM L.) (ARIZONA)." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188004.
Full textAbstract:
Pepper plants (Capsicum annuum L.) were grown in field and a greenhouse in Arizona to determine the effects of water stress, root temperature, and exogenously applied growth regulators on cytokinin production and the resulting growth. Research showed that vegetative plants were significantly higher in cytokinin activity and growth parameters than fruiting plants. Also, in root-pruned fruiting plants, cytokinin activity was less than that of intact fruiting plants. In vegetative plants, the competition between removed sinks and the rest of the shoot was reduced and, hence, more cytokinin came from the roots to the shoots. Besides, additional carbohydrates were available and recycled to the roots. In respect to temperature effect, elevating temperature from 15 to 30°C had a pronounced effect of increasing the growth rate and cytokinin activity. The measured parameters declined when temperature exceeded 30°C. Temperatures between 25 and 30°C were found to be optimum. Under experimental conditions, growth regulators (Cytex® and Burst®) applied to the soil or foliage had no significant effect on growth rates or cytokinin activity in roots. Also, applying Burst® or kinetin to the nutrient medium had inconsistent and statistically nonsignificant effects on photosynthesis and transpiration.
39
Alves, Leticia Rodrigues. "Biochemical and structural alterations induced by selenium under cadmium stress in tomato plants /." Jaboticabal, 2019. http://hdl.handle.net/11449/183154.
Full textAbstract:
Orientador: Priscila Lupino GratãoResumo: As plantas estão expostas a adversidades no ambiente que as circundam, como a contaminação por cádmio (Cd). Este metal pesado tem aumentado na atmosfera devido a atividades humanas. As plantas podem absorver o Cd, causando sérias alterações estruturais, fisiológicas e bioquímicas. As plantas desenvolveram sistemas de defesa complexos, incluindo mecanismos não enzimáticos e enzimáticos para evitar uma cascata de oxidação descontrolada causada pelo estresse oxidativo. Alguns elementos, como o selênio (Se), se utilizados em concentração adequadas, podem induzir uma melhora no sistema antioxidante, no crescimento e nos atributos fotossintéticos. Ainda é pouco conhecido o papel do Se nas respostas das plantas ao estresse. O objetivo deste trabalho foi obter novas informações sobre o papel do selenato e selenito no sistema de desintoxicação das plantas, incluindo a avaliação da nutrição mineral, atividade de enzimas antioxidantes e conteúdo de compostos não enzimáticos, pigmentos, alterações estruturais e o papel do Se na modulação do etileno, com o uso de mutantes hormonais como ferramenta. Nossos dados indicam que o Se é uma estratégia interessante para melhorar o metabolismo da planta sob condições normais ou estressantes. O selênio pode induzir aumento da ação do metabolismo de defesa antioxidante, provavelmente devido a alterações na sinalização do etileno. Além disso, em condições normais, o Se induz alterações estruturais nas células, o que pode contribuir para o desenvolvim... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Cadmium (Cd) contamination is a worldwide concern and one of the most severe causes of abiotic stress in plants, triggering losses in crop production and contamination risks to human health. This heavy metal increased in atmosphere due to human activities. Plants can uptake Cd, causing serious changes in structural, physiological and biochemical processes. Plants developed a complex defence systems including non-enzymatic and enzymatic mechanism to avoid oxidative stress and prevent an uncontrolled oxidation cascade. Some elements, such as selenium (Se), if used in adequate concentration, may induce an improvement in antioxidant system, growth and photosynthetic attributes. It is still unknown the mechanisms of Se in stress responses. The aim of this work was get new insights about the role of selenate and selenite-mediated detoxification strategies, including the evaluation of mineral nutrition, the activity of antioxidant enzymes and non enzymatic compounds, pigments, structural alterations and the role of Se in modulate ethylene, with the use of hormonal mutants as a tool. Our data indicates that Se is an interesting strategy to improve plant metabolism under normal or Cd stressful-condition. Selenium may induce enhancement in antioxidant defence metabolism, probably due to alterations in ethylene signalling. Moreover, under normal condition Se induce structural alterations in cells, which may contribute to plant development. Thus, the information available in this work is... (Complete abstract click electronic access below)
Doutor
40
Mathieson, I. C. "The physiology of plants as influenced by the incorporation into rooting media of refuse materials." Thesis, Open University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383661.
Full text
41
MU'ALLEM, ABUBAKER SALEM. "PHYSIOLOGICAL CHARACTERISTICS IN COTTON GENOTYPES AS AFFECTED BY PLANT AGE AND PLANTING DENSITIES." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184031.
Full textAbstract:
Physiological characteristics of three cotton genotypes were evaluated for their responses to plant aging under high and low planting density (HPD and LPD) treatments. In addition, the relationship of these physiological characteristics to fruit production were determined. Two genotypes are sympodia producing, "Pima S-6" (Gossypium barbadense L.) and "Deltapine 90" (DPL-90) (G. hirustum L.). The third, a "Cluster Selection" (G. barbadense L.) does not produce sympodia. These genotypes were grown on a Gila sandy loam soil at Tucson, Arizona in 1984 and 1985. Plant physiological characteristics were measured under field conditions at 5 intervals. Leaf physiological characteristics were determined at 7 different leaf ages. LPD treatment significantly reduced total dry weight (TDW), fruit dry weight (FDW), and leaf area index (LAI) in each genotype, but reductions were more pronounced in Pima S-6 and Cluster Selection in both seasons. However, LPD treatment significantly increased plant leaf area, but had no effect on specific leaf weight (SLW), petiole nitrate-nitrogen (Petiole NO₃-N) concentration, leaf area ratio (LAR), and fruiting index (FI), for all genotypes in both seasons. The aging patterns of all physiological characteristics were similar in both planting density treatments, regardless of genotype or season. Regression analyses showed that photosynthetic rate was curvilinearly correlated with leaf age (r² = 0.65 to 0.77, P < 0.01). However, petiole NO₃-N concentration decreased linearly with increasing leaf age (r² = 0.90 to 0.91, P < 0.01). Photosynthetic rate increased curvilinearly with increasing petiole NO₃-N concentration (r² = 0.61 to 0.79, P < 0.01). SLW was not correlated with leaf age, or other leaf physiological characteristics regardless of planting density treatment in 1985. TDW, FI, and LAI were directly related, while petiole NO₃-N concentration and LAR were inversely related to fruit production for all genotypes in both seasons. Multiple regression analyses showed that excluding planting density treatment effect, TDW, FI, and LAI were the most important variables incorporated for fruit prediction in both seasons.
42
Yang, Xiaomei Sibley Jeffrey Lynn. "Effects of a nonionic surfactant on plant growth and physiology." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Horticulture/Dissertation/Yang_Xiaomei_2.pdf.
Full text
43
Liu, Jiping. "Characterization and molecular cloning of sos3: A gene important for salt tolerance and potassium nutrition in higher plants." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/283921.
Full textAbstract:
The major goal of my dissertation research was to use genetic approaches to identify and characterize the components (genes) that are important for salt tolerance in Arabidopsis. Identification and characterization of such genes might provide insights into why these genes are important, and how these genes function in salt response and salt tolerance in higher plants. During my dissertation research, the sos3-1 mutant was isolated and characterized. The mutant plants are hypersensitive to Na⁺ and unable to grow with low K⁺. Increased Ca²⁺ levels can partially suppress the growth defect of the mutant plants under salt stress and fully restore their growth under low K⁺. These results suggest that SOS3 may be a Ca²⁺-mediated regulator that controls K⁺ and Na+ homeostasis in Arabidopsis. The SOS3 gene was cloned by map-based cloning techniques. SOS3 encodes a protein sharing significant sequence similarity with the B subunit of calcineurin from yeast and neuronal calcium sensor from animals. SOS3 contains three putative EF-hand calcium binding domains and a putative myristoylation motif at its NH₂-terminus. SOS3 binds calcium and is myristoylated in vitro. A mutation in SOS3 that destroys the conserved myristoylation motif abolishes SOS3 myristoylation, but not its calcium binding in vitro. Furthermore, the defect in Ca²⁺ binding of the sos3 does not affect its myristoylation. These results indicate the independence of calcium binding and myristoylation of SOS3. Mutant sos3-1 has a nine-base-pair deletion in the second conserved EF-hand Ca²⁺ binding domain, which leads to misfunction. of sos3 in vivo. To determine if myristoylation is also important for SOS3, the wild-type SOS3 cDNA and the SOS3 cDNA with a disrupted conserved myristoylation sequence were tested for their capability to complement the sos3-1. It was found that an intact conserved myristoylation sequence is essential for SOS3 function. These results indicate that both calcium binding and myristoylation are essential for the function of SOS3.
44
Masakapalli, Shyam Kumar. "Network flux analysis of central metabolism in plants." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:ac8b3836-9ab7-4060-b50a-df8aaa0e4ba5.
Full textAbstract:
The aim of this thesis was to develop stable-isotope steady-state metabolic flux analysis (MFA) based on 13C labeling to quantify intracellular fluxes of central carbon metabolism in plants. The experiments focus on the analysis of a heterotrophic cell suspension culture of Arabidopsis thaliana (L) Heynh. (ecotype Landsberg erecta). The first objective was to develop a robust methodology based on combining high quality steady-state stable labeling data, metabolic modeling and computational analysis. A comprehensive analysis of the factors that influence the outcome of MFA was undertaken and best practice established. This allowed a critical analysis of the subcellular compartmentation of carbohydrate oxidation in the cell culture. The second objective was to apply the methodology to nutritional perturbations of the cell suspension. A comparison of growth on different nitrogen sources revealed that transfer to an ammonium-free medium: (i) increased flux through the oxidative pentose phosphate pathway (oxPPP) by 10% relative to glucose utilisation; (ii) caused a substantial decrease in entry of carbon into the tricarboxylic acid cycle (TCA); and (iii) increased the carbon conversion efficiency from 55% to 69%. Although growth on nitrate alone might be expected to increase the demand for reductant, the cells responded by decreasing the assimilation of inorganic N. Cells were also grown in media containing different levels of inorganic phosphate (Pi). Comparison of the flux maps showed that decreasing Pi availability: (i) decreased flux through the oxPPP; (ii) increased the proportion of substrate fully oxidised by the TCA cycle; and (iii) decreased carbon conversion efficiency. These changes are consistent with redirection of metabolism away from biosynthesis towards cell maintenance as Pi is depleted. Although published genome-wide transcriptomic and metabolomic studies suggest that Pi starvation leads to the restructuring of carbon and nitrogen metabolism, the current analysis suggests that the impact on metabolic organisation is much less extreme.
45
Tucker, Sally Sue. "Morphological and physiological traits as indicators of drought tolerance in tallgrass prairie plants." Thesis, Kansas State University, 2010. http://hdl.handle.net/2097/4628.
Full textAbstract:
Master of ScienceDepartment of Biology
Jesse B. Nippert
The Konza Prairie in northern Kansas, USA contains over 550 vascular plant species; of which, few have been closely studied. These species are adapted to environmental stress as imposed by variable temperature, precipitation, fire, and grazing. Understanding which plant traits relate to drought responses will allow us to both predict drought tolerance and potential future shifts in plant community composition from changes in local climate. Morphological and physiological measurements were taken on 121 species of herbaceous tallgrass prairie plants grown from seed in a growth chamber. Gas exchange measurements including maximum photosynthetic rate, stomatal conductance to water vapor, and intercellular CO[subscript]2 concentration were measured. All plants were exposed to a drought treatment and were monitored daily until stomatal conductance was zero. At this point, critical leaf water potential (Ψ[subscript]crit), an indicator of physiological drought tolerance was assessed. Other measurements include root length, diameter, volume, and mass, leaf area, leaf tissue density, root tissue density, and root to shoot ratio. Traits were compared using pair-wise bivariate analysis and principal component analysis (PCA). A dichotomy was found between dry-adapted plants with thin, dense leaves and roots, high leaf angle, and highly negative Ψ[subscript]crit and hydrophiles which have the opposite profile. A second axis offers more separation based on high photosynthetic rate, high conductance rate, and leaf angle, but fails to provide a distinction between C[subscript]3 and C[subscript]4 species. When tested independently, grasses and forbs both showed drought tolerance strategies similar to the primary analysis. Matching up these axes with long term abundance data suggests that species with drought tolerance traits have increased abundance on Konza, especially in upland habitats. However, traits that relate to drought tolerance mirror relationships with nutrient stress, confounding separation of low water versus low nutrient strategies. My results not only illustrate the utility of morphological and physiological plant traits in classifying drought responses across a range of species, but as functional traits in predicting both drought tolerance in individual species and relative abundance across environmental gradients of water availability.
46
Mateo, Alfonso. "Roles of LESIONS SIMULATING DISEASE1 and Salicylic Acid in Acclimation of Plants to Environmental Cues : Redox Homeostasis and physiological processes underlying plants responses to biotic and abiotic challenges." Doctoral thesis, Stockholm University, Department of Botany, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-698.
Full textAbstract:
In the natural environment plants are confronted to a multitude of biotic and abiotic stress factors that must be perceived, transduced, integrated and signaled in order to achieve a successful acclimation that will secure survival and reproduction. Plants have to deal with excess excitation energy (EEE) when the amount of absorbed light energy is exceeding that needed for photosynthetic CO2 assimilation. EEE results in ROS formation and can be enhanced in low light intensities by changes in other environmental factors.
The lesions simulating disease resistance (lsd1) mutant of Arabidopsis spontaneously initiates spreading lesions paralleled by ROS production in long day photoperiod and after application of salicylic acid (SA) and SA-analogues that trigger systemic acquired resistance (SAR). Moreover, the mutant fails to limit the boundaries of hypersensitive cell death (HR) after avirulent pathogen infection giving rise to the runaway cell death (rcd) phenotype. This ROS-dependent phenotype pointed towards a putative involvement of the ROS produced during photosynthesis in the initiation and spreading of the lesions.
We report here that the rcd has a ROS-concentration dependent phenotype and that the light-triggered rcd is depending on the redox-state of the PQ pool in the chloroplast. Moreover, the lower stomatal conductance and catalase activity in the mutant suggested LSD1 was required for optimal gas exchange and ROS scavenging during EEE. Through this regulation, LSD1 can influence the effectiveness of photorespiration in dissipating EEE. Moreover, low and high SA levels are strictly correlated to lower and higher foliar H2O2 content, respectively. This implies an essential role of SA in regulating the redox homeostasis of the cell and suggests that SA could trigger rcd in lsd1 by inducing H2O2 production.
LSD1 has been postulated to be a negative regulator of cell death acting as a ROS rheostat. Above a certain threshold, the pro-death pathway would operate leading to PCD. Our data suggest that LSD1 may be subjected to a turnover, enhanced in an oxidizing milieu and slowed down in a reducing environment that could reflect this ROS rheostat property. Finally, the two protein disulphide isomerase boxes (CGHC) present in the protein and the down regulation of the NADPH thioredoxin reductase (NTR) in the mutant connect the rcd to a putative impairment in the reduction of the cytosolic thioredoxin system. We propose that LSD1 suppresses the cell death processes through its control of the oxidation-reduction state of the TRX pool. An integrated model considers the role of LSD1 in both light acclimatory processes and in restricting pathogen-induced cell death.
47
Oliveira, Juliano Rossi. "Alexander grass seed physiology and production: a step towards the conversion of a weed into a forage plant." Universidade Tecnológica Federal do Paraná, 2017. http://repositorio.utfpr.edu.br/jspui/handle/1/2327.
Full textAbstract:
CAPES; Fundação AraucáriaO papuã é uma espécie do gênero Brachiaria que apresenta elevado potencial de produção de forragem de alta qualidade. A planta é comumente encontrada no Sul do Brasil e tomada na maioria das vezes como uma invasora de cultivos de grãos, dado seu hábito de emergir espontaneamente do banco de sementes do solo. Vários estudos avaliaram o pastejo de papuã e confirmaram sua alta capacidade em produzir forragem, todavia, o uso apropriado da planta ainda está limitado pela falta de informações a respeito do seu comportamento reprodutivo, informações estas que poderiam (1) embasar o estabelecimento de um sistema de produção de sementes para disseminar a espécie como pastagem e, em contraponto, (2) apoiar o desenvolvimento de estratégias de controle quando a planta não é desejada. O objetivo deste trabalho foi compilar resultados de experimentos e revisões de literatura visando apresentar uma análise geral da fisiologia das sementes do papuã, desde o início do seu desenvolvimento até a dispersão. Características forrageiras foram ocasionalmente discutidas, com vistas a relacionar as conclusões ao comportamento sistemático da planta. A morfologia reprodutiva foi avaliada por meio de características como o número de inflorescências, a emergência das inflorescências ao longo do tempo, a ramificação da inflorescência, o número de sementes, o comprimento das inflorescências e dos racemos, o tempo e a intensidade da degrana, o sentido da degrana na panícula, entre outros; todas relacionadas com a idade das panículas. Ainda, a maturação e a germinação das sementes foram discutidas de acordo com componentes reprodutivos como o peso de mil sementes e a porcentagem de massa seca. Métodos de coleta foram comparados de acordo com a qualidade fisiológica da semente. As respostas da planta aos estímulos ambientais para germinação e indução floral foram apresentadas e teorizadas. Tratamentos para melhorar o desempenho e a qualidade das sementes e quebrar mecanismos de dormência foram testados, buscando estabelecer tanto manejos para a produção bem como entender as respostas bioquímicas das sementes. O comportamento do banco de sementes do solo é apresentado e por fim são feitas algumas considerações a respeito dos patógenos que atacam as sementes do papuã. Com base nas informações coletadas alguns rumos foram estabelecidos para o manejo de produção, colheita e plantio do papuã. A literatura encontrada tratando da espécie é vaga, todavia, experiências e dados apresentados para outras espécies de Brachiaria amplamente cultivadas para pastejo e produção de sementes no Brasil, serviram de suporte para as conclusões. De forma geral, o método de varredura é o mais apropriado para a colheita das sementes de papuã. O manejo de cortes de uniformização não influenciou a sincronia e a quantidades de panículas produzidas. A espécie produz grande quantidade de panículas por área, atingindo em torno de 1.750 panículas m-2. A degrana natural das sementes acontece de maneira rápida, 11 dias após a emergência das panículas em torno de 30% das sementes já se desprendeu, após 20 dias este valor sobe para em torno de 60% das sementes. A degrana também influencia na distribuição do peso de mil sementes ao longo da panícula. O papuã apresenta racemos menores, sementes menores, panículas mais longas e mais rácemos por panícula do que a maioria das Brachiarias comumente utilizadas no Brasil. A maturação e enchimento das sementes ocorre na mesma direção da degrana, acontecendo da parte distal para a parte proximal da panícula. Quanto maior o peso da semente, maior a germinação. Depois de seis meses de armazenamento um minuto de escarificação física usando um escarificador rotacional com lixa é suficiente para promover a germinação do papuã. A embebição do substrato de germinação com KNO3 na dose de 0.4% v.v. promove a germinação, e o uso de escarificação ácida com H2SO4 é deletério para a semente.
Alexander grass is a Brachiaria species with great potential to produce plentiful and high quality forage. It is broadly found in Southern Brazil, and taken most of the time as a weed given the habit to develop spontaneously in fields of grain crops. Several studies assessed grazing and confirmed its characteristics as a good forage plant, especially in integrated production systems. Regardless, its use stills limited by the lack of knowledge on reproductive traits that could (1) endorse the establishment of an organized seed production to spread it as a pasture and (2) help to design control strategies when the plant is not desired. The major aim of this work was to compile experiment results and literature review to provide a big picture on the Alexander grass seed physiology, from the seed development until the dispersal. Forage characteristics are also discussed to provide a systematic and complete understanding of the plant behavior. The reproductive morphology was assessed through quantitative traits such as the number of inflorescences produced, the seasonal timing of inflorescence production, branching of the inflorescence, number of seeds according to the inflorescence organs, inflorescence and racemes length, shattering timing, shattering speed, shattering intensity, and other characteristics according to the panicle age and the plant phenology. Maturation and germination of the seeds are discussed according to reproductive components such as thousand seed weight and seed dry mass percentage; relativized yet to the elapsing of the cycle. Seed gathering methods are compared according to the physiological quality of the seed and practicability. Plant response to environmental stimulus to flowering and germination are presented and theorized. Further, treatments to release dormancy and improve the seed performance were tested, looking to establish a production management and to understand the seed biochemical responses. Behavior of soil seed bank under environmental influences were reviewed and discussed, and seed borne pathogens i.e. potential microbiological threatens are presented. On the base of this information, some guidelines were established for the overall management to sow, produce and harvest Alexander grass. Scarce literature and data are found on the species. Fortunately, lessons and previous experience with Brachiaria widely used as pasture in Brazil helped the comparisons and supported the conclusions. It was found that ground-sweeping method is the most proper way to harvest Alexander grass seed. Defoliation management did not influence the synchrony and the amount of panicle emerged. Alexander grass presents high panicle production per area, reaching near 1,750 panicles m-2. Seed shattering starts rapidly, after 11 days from the panicle emergence near 30% of seed already shed, after 20 days near 60% of the seed already shed. Shattering also influences the distribution of the thousand seed weight along the panicle. Alexander grass presents smaller racemes, smaller seeds, longer panicles and more racemes per panicle than most of the Brachiariagrasses widespread in Brazil. Seed maturation and filling follows the same direction of the shattering, happening from the distal to the proximal fraction of the panicles (basipetally). Seeds threshed from the panicle present low germination and low shelf life. Generally, seeds present large variability even when collected from the ground. Seeds collected after the natural shatter present better germination than seeds collected directly from the panicle. The higher the thousand seed weight, the higher the seed germination. After six-month storage, one minute of physic scarification in a rotational machine with sandpaper was enough to promote the germination; Substrate imbibition with KNO3 at the dose of 0.4% promotes the germination and H2SO4 acid scarification is deleterious to the seed.
48
Smith, Andrew E. "The effect of enhanced ultraviolet-B radiation on the photosynthetic metabolism of terrestrial Antarctic plants." Thesis, Anglia Ruskin University, 2009. http://arro.anglia.ac.uk/581959/.
Full textAbstract:
The potential effect of increased UV-B radiation on photosynthetic activity and related processes in a range of terrestrial Antarctic plant species was investigated; from a chlorophyte alga to a vascular plant (Deschampsia antartica). The relative contribution of the UV-B waveband to photosystem II (PSII) damage was used to construct an action spectrum for those species found to be sensitive to UV-B exposure. Investigation involved non-invasive measurements of photosynthesis using chlorophyll-a fluorescence emission coupled with polarographic measurement of oxygen and infra-red gas analysis of carbon dioxide. Compounds associated with UV-B protection were extracted, and analysed using high performance liquid chromatography. Different species exhibited differing sensitivity to UV-B exposure. Reduction in the efficiency of the light independent stage of photosynthesis and decrease in leaf length were found in D. antarctica. A decline in the potential activity of PSII (dark-adapted chlorophyll-a fluorescence) was found in some cryptogams, but no concurrent decrease in gas exchange parameters. Shorter wavelengths of UV-B were shown to be more effective in depression of PSII efficiency. The first action spectrum for terrestrial Antarctic plants would predict a higher weighted UV-B exposure under ambient ozone, but would expect less damage under stratospheric ozone depletion than the commonly used plant action spectrum. Some of the plants investigated contained increased amounts of UV absorbing flavonoids following UV-B exposure. The morphological changes found in D. antarctica should lower photosynthetic productivity, but are dependent on developmental stage. The action spectrum produced herein would still forecast increased damage to PSII due to early spring ozone depletion, but not as great as previously predicted. Moreover, current levels of UV-B radiation may be more damaging to some species than previously thought based on other plant action spectra.
49
Wu, Qingyu. "Improvement of abiotic stress tolerance and calcium-deficiency disorder resistance of tomato plants." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/14033.
Full textAbstract:
Doctor of PhilosophyDepartment of Horticulture, Forestry, and Recreation Resources
Sunghun Park
Plants are continuously exposed to numerous abiotic stresses, which adversely affect plant growth, development, and yield. Plants have developed different signaling pathways to cope with abiotic stresses, and some of the pathways converge to help plants tolerate simultaneous stresses. Here, we report ectopic expression of an Arabidopsis glutaredoxin AtGRXS17 that confers tolerance to multiple abiotic stresses in tomato plants. In yeast assays, AtGRXS17 co-localized with yeast ScGrx3 in the nucleus and suppressed the sensitivity of yeast grx3grx4 double mutants to oxidative stress and heat shock. In plants, GFP-AtGRXS17 fusion proteins initially localized in the cytoplasm but migrated to the nucleus during heat stress. Ectopic expression of AtGRXS17 in tomato plants minimized photo-oxidation of chlorophyll and reduced oxidative damage of cell membrane systems under heat stress. Furthermore, expression of the heat shock transcription factor (HSF) and heat shock protein (HSP) genes was up-regulated in AtGRXS17-expressing tomato plants during heat stress when compared to wild-type controls. Under cold, drought, and oxidative stress conditions, AtGRXS17-expressing tomato plants also displayed more vigorous growth and less physiological damage than those of the wild-type control plants. Quantitative real-time PCR (qRT-PCR) analysis indicated that expression of AtGRXS17 alters multiple stress defense signaling pathways, including the Abscisic Acid (ABA) and C-Repeat Binding Factors (CBF) pathways. The results revealed a conserved function for a glutaredoxin protein in abiotic stress adaptation, and manipulation of AtGRXS17 may be a useful approach to improve crop stress tolerance and understand plant signaling under abiotic stress conditions. Deregulated expression of an Arabidopsis H[superscript]+/Ca[superscript]2[superscript]+ antiporter (sCAX1) in agricultural crops increases total calcium (Ca[superscript]2[superscript]+) but may result in yield loses due to calcium-deficiency like symptoms. Here we demonstrate that co-expression of a maize calreticulin (CRT, a Ca[superscript]2[superscript]+ binding protein located at endoplasmic reticulum) in sCAX1-expressing plants mitigated these adverse effects while maintaining enhanced Ca[superscript]2[superscript]+ content. Co-expression of CRT and sCAX1 could alleviate the hypersensitivity to ion imbalance in tobacco plants. Furthermore, blossom-end rot (BER) in tomato may be linked to changes in CAX activity and enhanced CRT expression mitigated BER in sCAX1 expressing lines. These findings suggest that co-expressing Ca[superscript]2[superscript]+ transporters and binding protein at different intracellular compartments can alter the content and distribution of calcium within the plant matrix.
50
Larkindale, Jane. "Cell signalling in response to heat shock in Arabidopsis thaliana." Thesis, University of Oxford, 2001. http://ora.ox.ac.uk/objects/uuid:dc24f743-a69b-4aa9-92a4-fbdcbcff2bef.
Full textAbstract:
Increases in temperature damage plant cells, and plants react to heat stress by inducing of a number of protective mechanisms. In this study, it has been shown that heat damages cells both directly while the plants are being heated, and indirectly through heat induced oxidative stress during recovery from heating. Different stress response pathways are induced in each case. Evidence implicates salicylic acid, abscisic acid, ACC (a precursor of ethylene), calcium ions and active oxygen species in pathways resulting in thermotolerance (i.e. increased survival at high temperature). Addition of these potential second messengers results in increased survival and decreased oxidative damage after heating (as measured using the TBARS assay), while silencing the pathways through use of mutants, inhibitors or transgenes results in decreased thermotolerance. In vivo calcium measurements show cytosolic calcium transients only at initiation of cooling after heat stress. Calcium chloride also induces thermotolerance when added after heating, as does ACC. These substances can induce early increases in ascorbate peroxidase activity after heating, and induce expression of antioxidant genes. Thus they may play a role in heat induced oxidative stress response pathways in recovery. Two different pathways induced during heating appear to result in the expression of genes for heat shock proteins. The predominant pathway induced at 30oC involves ABA, while that at 35-40oC involves an oxidative burst generated through the NADPH oxidase, atrbohB. Addition of SA can induce HSP (heat shock protein) expression, but there is little evidence that this occurs endogenously in plant cells, although nahG plants unable to signal via SA are thermosensitive. Results in this study indicate that there are several signalling pathways associated with heat shock. The pathway induced during recovery from heating involves calcium ions and ethylene, and results in increased antioxidant capacity. During heating two pathways induce expression of HSPs: one involving abscisic acid and possibly salicylic acid and one involving an oxidative burst. At least one further pathway is believed to exist, which involves protein kinases and phosphatases as heat shock causes up-regulation of expression of certain genes for these signalling components.