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1
Peacock, Kenneth. "Growth, mechanical stress responses and mutation of sunflower seedling hypocotyls." Thesis, University of Aberdeen, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277289.
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The aims of this thesis were four-fold: 1. To characterise the patterns of growth underlying established nutations of etiolated sunflower seedling hypocotyls. 2. To characterise the growth patterns and events surrounding the initiation of nutation in etiolated sunflower seedling hypocotyls. 3. To investigate the effects of applied compression and tension forces on the straight growth of etiolated sunflower seedling hypocotyls. 4. To investigate the relationship between auxin and the responses to mechanical stress in etiolated sunflower seedling hypocotyls. Time-lapse video analysis showed that the growth of etiolated sunflower seedling hypocotyls was more dynamic than expected, with growth constantly changing. When growth rates were plotted against time, the resultant curves showed regular oscillations similar to those of the movement traces for nutation and it was apparent that the nutational movements were intimately linked to the patterns of growth. Such patterns of growth were also found prior to the onset of nutation but in that case the growth curves on opposite sides of the hypocotyl did not oscillate out of phase with each other until immediately before the start of nutation. It was also found that there was a threshold height below which nutations were never found. The roles of light and geotropic responses in the initiation of nutation were also investigated. It was found that light was not required for nutation to occur and that various types of geotropic stimulation failed to initiate nutation in seedlings below the threshold height, although such seedlings were capable of responding to a gravity stimulus. It was concluded that the initiation and maintenance of nutation is an endogenous process and that nutation is a result of the way in which seedling hypocotyls grow rather than a discrete phenomenon superimposed on `normal' growth. The application of compression forces increased the growth of etiolated sunflower seedling hypocotyls over that of the non-compressed controls while tension forces applied to the same material did not produce any significant change in growth rates. When compression forces were applied to seedlings immersed in 10-10 Molar auxin solution the increase in growth due to compression were larger than those found for seedlings compressed while immersed in distilled water. It was concluded that some mechanism for the reception of compression forces operates in this material possibly involving a change in the sensitivity of the epidermal cells to auxin. A model was proposed in which growth is controlled by the mechanical forces acting on individual cells. It is suggested that nutation arises from the responses of cells and groups of cells to such mechanical strains.
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Myers, Jonathan Andrew. "Seedling carbohydrate storage, survival, and stress tolerance in a neotropical forest." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0009262.
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Ye, Nenghui. "Stress perception and ABA signaling in rice seed germination and seedling establishment." HKBU Institutional Repository, 2011. https://repository.hkbu.edu.hk/etd_ra/1305.
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Liu, Rui. "Regulation and molecular signaling during seed germination and seedling establishment of arabidopsis in response to abiotic stresses." HKBU Institutional Repository, 2013. https://repository.hkbu.edu.hk/etd_oa/101.
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Plants regulate many physiological processes in response to adverse environmental stresses. This study focused on the seed germination and seedling establishment stage and investigated the molecular signaling events when abiotic stresses, such as osmotic, water and temperature, were applied. Seeds of Arabidopsis, mutants or wild type, were used to identify the signaling components. Cold-pretreatment (stratification) is widely used to break seed dormancy and improve germination rate. Stratification at 4. significantly broke the seed dormancy of Arabidopsis in wild-type, cyp707a2, sleepy1 and sleepy1/cyp707a2, but not in ga3ox1. Stratification and exogenous ABA treatment strongly enhanced the expression and the activity of a-amylase in the freshly harvested seeds among the wild-type and those mutants, which have relatively high ABA content. Similarly, the expression of RGL2 and ABI5 were also substantially suppressed by stratification. These results suggest that stratification firstly leads to GA biosynthesis and unlocks the inhibition of RGL2 on the expression of a-amylase. Stratification also relieves the inhibition of ABA on the germination process but the inhibition of ABA on seedling development is not affected. We have isolated an Arabidopsis mutant, dsptp1, which is hyposensitive to osmotic stress during seed germination and seedling establishment, indicated by exhibiting higher seed germination rate, lower inhibition in root elongation under osmotic stress, and more tolerance to drought compared with the wild type (Col0) plants. Osmotic stress and drought enhanced AtDsPTP1 expression in seed coats, the bases of rosette leaves and roots. Compared with the wild type, the dsptp1 mutant increased proline accumulation, reduced MDA content and ion leakage, and enhanced antioxidant enzyme activity under osmotic stress. AtDsPTP1 regulated the transcript levels of various dehydration responsive genes, ABA biosynthesis and metabolic enzyme gene under osmotic stress, resulting in reduced accumulation of ABA in dsptp1 mutant plants than wild type in response to osmotic stress. AtDsPTP1 also mediated the ABA signaling pathway under osmotic stress by suppressing the expression of ABI1 and enhancing the expression of the positive regulators ABI3 and ABI5 in ABA signaling. These data suggest that AtDsPTP1 positively regulates ABA accumulation and signaling during seed germination and seedling establishment in Arabidopsis under osmotic stress. To further investigate the regulation mechanism of DsPTP1 in osmotic stress and drought signaling, we analyzed the water holding capacity between wild type and dsptp1 mutant. The dsptp1 mutant exhibited enhanced water holding capacity compared to wild type under osmotic stress resulting from reduced water loss and increased relative water content, which shall contribute the osmotic and drought tolerance. To identify the signaling components, we investigated the activity of MAPKs under osmotic and drought stress and found that the DsPTP1 differentially regulates the activities of MAPK6 and a p38 MAPK, which is inferred as MAPK12 according to its molecular weight in Arabidopsis under osmotic and salt stress. However, there is no direct interaction between DsPTP1 and 20 MAPKs indicated by the results of the of specific interaction test. These results suggest that the differential regulation of MAPK6 and MAPK12 by DsPTP1 is indirect. In addition, we screened the interaction proteins of DsPTP1 under abiotic stress. Seventeen positive clones were acquired from the sequencing results. More work need to be done to confirmed the positive interactions and the signaling cascades. In summary, seed germination and seedling growth are closely regulated by environmental cues. This should be the result of evolutionary selection since successful new growth from the seed embryo depends on the sensitive perception of environmental conditions and effective regulation of many physiological processes that are involved. We have demonstrated that plant hormones, especially ABA, play central regulative roles during such regulations. Many other signaling components, such as protein kinases and phosphatases, are also involved. Identifying the detailed signaling pathways should be the focus of further research.
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Nkomo, Mbukeni Andrew. "The role of p-coumaric acid on physiological and biochemical response of chia seedling under salt stress." University of the Western Cape, 2020. http://hdl.handle.net/11394/7954.
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Philosophiae Doctor - PhD<br>The role of phenolic acids in mitigating salt stress tolerance have been well documented. However, there are contradicting reports on the effect of exogenously applied phenolic acids on the growth and development of various plants species. A general trend was observed where phenolic acids were shown to inhibit plant growth and development, with the exception of a few documented cases. One of these such cases is presented in this thesis. This study investigates the role of exogenously applied p-coumaric acid (p-CA) on physio-biochemical and molecular responses of chia seedlings under salt stress. This study is divided into three parts. Part one (Chapter 3) focuses on the impact of exogenous p-coumaric acid on the growth and development of chia seedlings. In this section, chia seedlings were supplemented with exogenous p-CA and the various biochemical and plant growth parameters were measured. The results showed that exogenous p-CA enhanced the growth of chia seedlings. An increase in chlorophyll, proline and superoxide oxide contents were also observed in the p-CA treatment relative to the control. We suggested that the increase in chia seedling growth could possibly be via the activation of reactive oxygen species-signalling pathway involving O2− under the control of proline accumulation (Chapter 3). Given the allopathy, nature of p-coumaric acid it is noteworthy that the response observed in this study may be species dependent, as contrasting responses have been reported in other plant species. Part two (Chapter 4) of this study investigates the influence of piperonylic acid (an inhibitor of endogenous p-coumaric acid) on the growth and development of chia seedlings.
In trying to illustrate whether p-CA does play a regulatory role in enhancing pseudocereal plant growth, we treated chia seedlings with the irreversible inhibitor of C4H enzyme, to inhibit the biosynthesis of endogenous p-CA. In this section, chia seedlings were treated with piperonylic acid and changes in plant growth, ROS-induced oxidative damage, p-CA content and antioxidant capacity was monitored. Inhibition of endogenous p-CA restricted chia seedling growth by enhancing ROS-induced oxidative damage as seen for increased levels of superoxide, hydrogen peroxide and the extent of lipid peroxidation. Although an increase in antioxidant activity was observed in response to piperonylic acid, this increase was not sufficient to scavenge the ROS molecules to prevent oxidative damage and ultimate cellular death manifested as reduced plant growth. The results presented in this section support our hypothesis that p-CA play an important regulatory role in enhancing chia seedling growth and development as shown in Chapter 3. Part three (Chapter 5) seeks to identify and functionally characterise p-coumaric acid induced putative protein biomarkers under salt stress conditions in chia seedlings.
Previous studies have shown that p-CA reversing the negative effect caused by NaCl-induced salt stress. While these studies were able to demonstrate the involvement of p-CA in promoting plant growth under salt stress conditions, they focussed primarily on the physiological aspect, which lacks in-depth biochemical and molecular analysis (ionomic and proteomic data) which could help in detecting the genes/proteins involved in salt stress tolerance mechanisms. A comparative ionomics and proteomic study was conducted, with the aim of elucidating the pivotal roles of essential macro elements and/or key protein markers involved in p-CA induced salt stress tolerance in chia seedlings. With the exception of Na, all the other macro elements were decreased in the salt treatment. Contrary to what was observed for the salt treatment most of the macro elements were increased in the p-CA treatment. However, the addition of exogenous p-CA to salt stressed seedlings showed an increase in essential macro elements such as Mg and Ca which have been shown to play a key role in plant growth and development. In the proteomic analysis we identified 907 proteins associated with shoots across all treatments. Interestingly, only eight proteins were conserved amongst all treatments. A total of 79 proteins were unique to the p-CA, 26 to the combination treatment (NaCl + p-CA) and only two proteins were unique to the salt stress treatment. The unique proteins identified in each of the treatments were functionally characterised to various subcellular compartments and biological processes. Most of the positively identified proteins were localised to the chloroplast and plays key roles in photosynthesis, transportation, stress responses and signal transduction pathways. Moreover, the protein biomarkers identified in this study (especially in the p-CA treatment) are putative candidates for genetic improvement of salt stress tolerance in plants.
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Hosseini, Mohammad Khajeh. "The response of soybean seeds to the stresses of semi-arid environments during germination and early seedling growth." Thesis, University of Aberdeen, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324912.
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Reduced water availability and salinity are two major environmental factors influencing crop establishment in semi-arid environments. Therefore the effect of reduced water availability using polyethylene glycol (PEG) 4000 solutions and of salinity (NaCl) on the germination of six soybean cultivars was examined. Cultivars differed in their response to reduced water availability and salinity and in their ability to recover from the stresses. A large increase in germination during a recovery period at 0 MPa following water stress suggested that PEG was not toxic whilst the failure of seeds to recover from high salinity revealed the toxic effects of NaCl. At the same water potential, germination in saline conditions was higher than that in PEG and the rate of water uptake by individual seeds was more rapid in NaCl solutions than in PEG. The most plausible explanation for the greater water uptake and germination in NaCl is that seeds accumulated salts which lowered their osmotic potential. The effects of NaCl on seedling growth were much greater when experiments were conducted in a hydroponic system compared with a paper towel method. However, analysis of the solutions soaking the paper towels revealed that 4.25<I> </I>mMolal Ca2<sup>+</sup> was available to the seeds in this system in saline conditions. This may have reduced Na<sup>+</sup> uptake or provided a protective effect against Na<sup>+</sup> toxicity. Germination (40%) was possible at a tissue Na<sup>+</sup> concentration in the embryonic axis of 9.3mg g-1 FW whilst seedling growth was completely inhibited at a tissue Na<sup>+</sup> concentration of 6.1 mg g<sup>-1 </sup>FW. Germination at higher tissue Na<sup>+</sup> concentrations was associated with higher K<sup>+</sup>+Ca2<sup>+</sup> concentrations, suggesting that these ions may protect the seeds in the pregermination phase against salinity. A reduction in seed vigour due to ageing resulted in reduced germination under saline conditions compared to the germination of unaged seeds, but there was no significant interaction between salinity and seed ageing. However, unaged seeds showed a greater increase in germination after transfer to 0 MPa than did the aged seeds. Since both the site of ageing and the toxic effect of NaCl is the cell membrane, there may be additive effects of NaCl toxicity on cell membrane in aged seeds.
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Van, Tonder N. C. P., der Westhuizen C. Van, and der Westhuizen R. J. Van. "Interaction effects of effective microorganisms and prolonged storage on germination and seedling vigour of maize, sorghum and sunflower." Journal for New Generation Sciences, Vol 12, Issue 2: Central University of Technology, Free State, Bloemfontein, 2014. http://hdl.handle.net/11462/666.
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Published Article<br>A study involving two incubation experiments and a germination experiment in sandy soil was conducted to determine the influence of Multiplied Effective Micro-organisms (M-EM) that were exposed to different levels of irradiation and temperature fluctuation as well as prolonged storage, on the germination and seedling vigour of maize, sorghum and sunflower. Irrespective of poor handling and/or prolonged storage of M-EM, seed treatment with M-EM improved germination under optimal conditions for all crops compared to the control. Increased planting depths and cold stress were used to create conditions where seed treatment with M-EM may improve germination and seedling growth. Seed treatment with M-EM significantly improved germination and seedling vigour of the stress-tolerant maize cultivar following cold stress. Similar improved seedling vigour results were observed for the stress-tolerant sunflower cultivar at increased planting depth. It was concluded that the beneficial influence of M-EM as a seed treatment was remarkable, even after exposure of M-EM to unfavourable environmental conditions and prolonged storage before application. Further research under field conditions and in different cultivation systems are required before the large scale application of M-EM as seed treatment can be recommended.
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Ertle, John Michael. "Effects of Short-term Chilling Stress on Seedling Quality and Post-transplanting Growth of Grafted and Nongrafted Watermelon." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1594742774066127.
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Gurmu, Mulugeta. "The effects of seed vigour and moisture stress on the germination and seedling establishment of wheat and sorghum." Thesis, University of Aberdeen, 1991. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU031802.
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The experiments reported in this thesis assessed vigour differences between seed lots of wheat and sorghum under suboptimal conditions. A vigour assessment for each lot of both species was quantified by calculating a value for the viability equation constant Ki. Imbibition of seed lots at lower water potentials reduced water uptake, radicle and coleoptile emergence and their subsequent extension. Similarly, seeds aged by controlled deterioration also resulted in reduced radicle and coleoptile emergence and growth compared to that of unaged seeds. The critical water potential for radicle emergence, coleoptile emergence and their subsequent extension was lower for sorghum than that required for wheat. In both species coleoptile emergence and its subsequent extension was more sensitive than radicle emergence and extension. Tolerance of desiccation of both species decreased as germination progressed. However, imbibition of seeds for 24 h and drying back to their original moisture content promoted seed invigoration in some cases. Cells from seminal roots of wheat and sorghum were shorter when imbibed in lower water potentials than when they were imbibed at higher water potentials. The high drought tolerant cv (DJ1) showed lower root solute potential than the low drought tolerant cv (IS9). The results discussed in this thesis indicate that the information derived from controlled deterioration might be used as an indicator of planting value under sub-optimal conditions.
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Venn, Susanna Elizabeth, and Susanna Venn@nt gov au. "Plant recruitment across alpine summits in south-eastern Australia." La Trobe University. School of Life Sciences, 2007. http://www.lib.latrobe.edu.au./thesis/public/adt-LTU20080526.160815.
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This thesis investigated aspects of plant recruitment across an altitudinal gradient of mountain tops in the Victorian Alps, Australia, and provides a baseline for the patterns and processes of alpine plant recruitment in the absence of large-scale disturbance.
The patterns in alpine vegetation across the study sites were described in relation to abiotic environmental factors. Temperatures were lower and precipitation was higher at the high altitude sites. The vegetation did not differ significantly between the sites, although sites at low altitudes were shrubbier than those at high altitudes. Analysis of the soil seed bank revealed high mean densities of germinable seed (80 to 1400 seeds m-2) across the gradient of sites. The similarity between the seed bank samples and the standing vegetation was low (qualitative similarity: 0.08 to 0.2; quantitative similarity: 0.03 to 0.19).
In laboratory germination experiments, I found rapid and substantial germination. Final percent germination was above 90% for most species. One species, Aciphylla glacialis, showed evidence of dormancy mechanisms. In subsequent experiments, I found that innate primary seed dormancy in this species could be broken with cold-wet stratification.
There were no significant patterns in natural seedling recruitment across the altitudinal gradient. Similarities between the seedling flora and the standing vegetation
were low (qualitative similarity: 0.18 to 0.45: quantitative similarity 0.04 to 0.09). Mean seedling density was best predicted by a combination of soil wilting point, altitude and plant litter. In some cases, seedling density was greater than 80 seedlings m-2.
The relative importance of either negative (competitive) or positive (facilitative) interactions between seedlings with adjacent vegetation were investigated in relation to seed germination, seedling growth and seedling survival. Facilitative interactions were common at the higher altitude sites. At lower altitudes, facilitative and competitive interactions were common. Without close neighbours at high altitudes, seedlings were unlikely to survive into their second year.
An understanding of plant recruitment can provide a useful basis for predicting species responses to large-scale disturbance and climate change.
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Kibret, Kidist Bogale [Verfasser]. "Systems biological analysis of seedling vigour and osmotic stress tolerance in oilseed rape (Brassica napus L., Brassicaceae) / Kidist Bogale Kibret." Gießen : Universitätsbibliothek, 2017. http://d-nb.info/113657008X/34.
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Mills, Samuel John Alan Restall. "Potential of exogenous L-amino acids in salinity stress alleviation during germination and early post-germinative seedling growth of Lactuca sativa L." Thesis, University of Canterbury. Biological Sciences, 2014. http://hdl.handle.net/10092/10060.
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Soil salinity is a common abiotic stress for plants, that is having an increasing impact on international food production. A practical strategy to help mitigate the adverse effects of salinity stress on crop productivity is to increase salt tolerance of crop plants. It has been shown that exogenous application of L-proline and L-glutamate is capable of reducing the severity of salinity stress on seed germination and early seedling growth of brassica and cucumber, respectively. The main aim of the present study was to investigate the potential of all 20 common protein amino acids to alleviate salinity stress in lettuce (Lactuca sativa L., variety ‘Great Lakes’) during and immediately following germination. Sowing lettuce seeds in different concentrations of sodium chloride (NaCl) adversely affected germination and early seedling growth in a dose-dependent manner. After 48 hours of sowing lettuce seeds in 1 mM of any of the 20 exogenous amino acids in the absence of NaCl, it was found that the amino acids also inhibited seedling growth, particularly root elongation. However, in direct treatment experiments involving addition of seven amino acids singly (L-asparagine, L-isoleucine, L-leucine, L-proline, L-phenylalanine, L-tyrosine and L-valine) to an inhibitory concentration (60mM) of NaCl, it was found that lettuce seedling growth was protected from the salt stress. Additionally, seeds pre-treated for 8 hours before germination with L-arginine, L-glycine, L-histidine, L-methionine and L-phenylalanine, showed significant growth recovery after a further 40 hours growth exposed to 60mM NaCl.
The measurements of cell size in root maturation zone and mitotic index at the root tip of lettuce seedlings after 48 hours from sowing seeds suggested that it might be possible that some amino acid treatments could affect cell elongation and / or cell division. However, further in-depth investigations are required and warranted to elucidate the mechanism(s) whereby exogenous amino acids could play a role in alleviation of salt stress in lettuce. It is concluded that several L-amino acids have the potential in pre-sowing seed treatment (seed priming technology) to enhance salt tolerance for crop stand establishment in soils with salinity issues.
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Groninger, John William. "Stand dynamics and gas exchange in loblolly pine and hardwood seedling stands : impact of elevated carbon dioxide, water stress and nutrient status /." Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-08272007-163923/.
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Schnaithmann, Florian [Verfasser], Klaus [Akademischer Betreuer] Pillen, and Gunter [Akademischer Betreuer] Backes. "Mapping of quantitative trait loci regulating nitrogen stress tolerance and leaf rust seedling resistance in two selected populations derived from crosses between exotic and elite barley : [kumulative Dissertation] / Florian Schnaithmann ; Klaus Pillen, Gunter Backes." Halle, 2016. http://d-nb.info/1116951517/34.
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Ellsworth, Todd, David Robinson, and Albert Dobrenz. "PEG-Induced Stress on Alfalfa Seedlings." College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/203793.
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Muhamed, Hassan. "Le rôle des interactions biotiques dans la régénération des chênes au niveau des communautés de forêts dunaires de la région Aquitaine (Sud-Ouest de la France)." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14576/document.
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Bien que les interactions biotiques soient connues pour être déterminantes dans l’établissement des espèces, il est encore difficile de savoir quels facteurs sont impliqués dans l’équilibre entre interaction positive et interaction négative. Il est de fait difficile de savoir sous quelles conditions les interactions biotiques peuvent favoriser ou empêcher la régénération des espèces. Cette thèse vise à étudier le rôle des interactions biotiques d'arbustes avec des semis de chêne sur la régénération de trois espèces de chênes sur les forêts des dunes côtières d'Aquitaine en testant comment l’effet net de ces interactions varie le long d’un gradient d’aridité, sur deux étages de canopée et en fonction des stratégies fonctionnelles de trois espèces de Chêne dans un contexte de changement global. Ce travail a été effectué en utilisant deux approches, une approche descriptive en utilisant un patron de points répartis dans l’espace et une approche expérimentale en transplantant les semis cibles. Les résultats montrent que la variation spatiale, en terme d’interactions biotiques, est fortement corrélée avec la sévérité environnementale, avec des interactions entre jeunes pousses de chêne très sensibles aux sécheresses estivales et aux trouées dans les canopées. Les interactions testées étaient de nature facilitatrice dans les plots découverts dans les dunes sèches du nord de Soulac et tournaient à la compétition sous le couvert forestier dans les dunes plus humides du sud, à Seignosse. La nature des interactions était constant entre les stratégies fonctionnelles des espèces cibles de chêne. Les résultats de cette thèse montrent de manière générale une confirmation de la formulation originale du SGH qui prédit une augmentation de la facilitation en lien avec une augmentation de la sévérité environnementale et souligne le fait que la réduction du stress hydrique atmosphérique par des arbustes est nécessaire à la régénération des semis de chêne. Dans cette perspective, le sylviculteur doit conserver les arbustes du sous-étage, en particulier dans les trouées, afin de permettre une meilleure régénération des plants de chêne. Cette thèse met en évidence la nécessaire considération des interactions biotiques dans la régénération du chêne dans les actuelles sévères conditions climatiques et le rôle prépondérant de ces interactions dans la réponse aux changements climatiques futurs probables dans cette région Aquitaine<br>Although biotic interactions are known to be important determinants of species establishment, it is uncertain what factors determine the net balance between positive and negative interactions thus, under what conditions biotic interactions could enhance or impede species regeneration. Bien que les interactions biotiques soient connues pour être This thesis aims to study the role of biotic interactions of shrubs with oak seedlings for regeneration of three oak species on the Aquitaine coastal dune forests, by testing how the net effect of these interactions vary along aridity gradient, between two overstory canopies and in respect to the functional strategies of three oak species in the context of climate change. This was done by using two approaches, descriptive approach using spatial point pattern data and experimental approach by transplanting the target seedlings. The results show that the spatial variation in the nature of biotic interactions is strongly relate to environmental severity conditions, where the shrub-oak seedling interactions were very sensitive to increasing summer drought and canopy opening, the interactions strength was facilitative under gap plots in the dry northern dunes in Soulac and switch on competitive under forest plots in the wet southern dunes in Seignosse. The nature of the interactions was constant across the functional strategies of the targets species of oak. For the most part, results of this thesis show general support to the original formulation of SGH which predicts increasing facilitation with increasing severity and underscore the fact that atmospheric water stress reduction by shrubs is required for oak seedling regeneration. In this perspective, silviculturist should conserve understory shrubs, in particular in gaps, in order to allow a better regeneration niche of oak seedlings. This thesis highlights the importance of considering biotic interactions in oak regeneration under current harshness climatic conditions and with expectation to have an ambitious role in alleviation future climatic change consequence in this region
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Vaughan, David. "Characterisation of the plant cell wall under cold stress." Thesis, University of York, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251815.
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French, Robert John. "Leaf senescence and water stress in wheat seedlings /." Title page, contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09PH/09phf875.pdf.
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Sethar, Mumtaz Ali. "A physiological study of heat stress in cotton seedlings." Thesis, Bangor University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332035.
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Sopher, Coralie Rachelle. "Paclobutrazol-induced changes associated with stress protection in maize seedlings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ33276.pdf.
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Passos, Leonidas Paixao. "Growth and water status responses of mung bean (Vigna mungo L.) and other dicot species to osmotic stress." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184668.
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Intact dark- and light-grown mung bean (Vigna mungo L.), black bean (Phaseolus vulgaris L.), pea (Pisum sativum L.) cowpea (Vigna unguicul a ta (L.) Wa lp.) and squash (Cucurbita pepo L.) seedlings on hydroponic medium were osmotically stressed by exposing their roots to PEG 8000 of various concentrations (-0.2 to -0.6 MPa) to determine stress effects on growth and tissue water status. Growth of dark-grown mung bean hypocotyls ceases within 40 sec upon exposure to any level of stress, and resumes within 10 to 45 min. Growth of all other seedlings were measured usually after 3 to 24 h stress, and in 3 h, elongation is inhibited in dark-grown and is stopped in light-grown tissues. In dark-grown mung bean, black bean and squash hypocotyls and pea epicotyls, growth rates after 24 h stress were found to be proportional to the Ψ of the medium. In mung bean hypocotyls, growth stopped before any change in Ψ or Ψ(π) occurred in the growing region. In this tissue and also in dark-grown squash hypocotyls, pea epicotyls, and in lightgrown cowpea hypocotyls, equivalent reductions in Ψ and Ψ(π) were evident in the growing region after 3 h, so turgor remained constant. In other species, osmotic adjustment with turgor maintenance was evident after 24 h in both the growing and expanded regions. The results with mung bean hypocotyls provided the first demonstration that stress causes an almost instantaneous stress-caused cessation of elongation in dicots. Since data from all plants showed that stress causes growth rate inhibition or cessation without a concomittant decrease in Ψ(p), it is concluded that turgor is not the factor regulating growth. More likely, stress-caused growth and water status changes are responses to an earlier signal, such as a stress-caused reduction in the apoplastic Ψ.
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Sayed, Saud Saeed. "Studies of water-stress induced senescence and abscission in cotton seedlings." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305826.
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Bracher, Grant Allan. "Detection of nutrient stress in Douglas-fir seedlings using spectroradiometer data." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30961.
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Narrow-band spectral reflectance measurements in the visible and near-infrared region of the spectrum were investigated for the detection of nutrient deficiencies, and estimating the foliar concentrations of nitrogen, phosphorus, sulphur, and total chlorophyll. One-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were treated with 24 nutrient solutions containing nitrogen, phosphorus and sulphur levels ranging from 1 to 400 mg/L. After one growing season, newly matured needles were harvested, spectral reflectance measured from 400 to 1100 nm, and foliar samples analyzed for nutrient and chlorophyll levels.
Several nutrient deficiencies were diagnosed. There were no unique changes in spectral reflectance which could be attributed to a specific nutrient deficiency; rather changes in reflectance were non-specific responses influenced by how varying nutrient levels affected total chlorophyll concentration. All deficiencies caused decreases in total chlorophyll, thus demonstrating the value of total chlorophyll as an indicator of nutrient stress.
Correlation coefficients were calculated describing the degree of association between foliar nitrogen, phosphorus, sulphur and total chlorophyll, and the following spectral parameters: the wavelength of the red edge, percent spectral reflectance at 554 and 630 nm (red rise), and 15 vegetation indices (VIs). VIs were first determined using combinations of spectral reflectances at 480, 554, 800 nm and the wavelength of the red well (674 nm; called red well
VIs), and then recalculated using red rise (called red rise VIs) rather than red well measurements to see if greater correlation with foliar constituents could be obtained. Although the use of red rise measurements in the calculation of VIs 1, 2, 3, 12 and 14 resulted in higher correlation coefficients, differences between coefficients were seldom statistically significant.
Red well and red rise VI15 were most correlated with the needle nitrogen content of individual Douglas-fir, red rise VI10 with phosphorus, and spectral reflectance at 554 nm and red well VI15 with total chlorophyll. These parameters proved useful indicators of relative nitrogen, phosphorus and total chlorophyll content. None of the VIs or other spectral parameters followed the same relationship with foliar sulphur for the sulphur, nitrogen and phosphorus treatments; consequently, none were deemed suitable for sulphur estimation.<br>Forestry, Faculty of<br>Graduate
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Sarkar, Sunita. "Relationship between gibberellins, height and stress tolerance in barley (Hordeum vulgare L.) seedlings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ56695.pdf.
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Alaib, M. A. "Seedlings' growth in response to drought stress and 2,4-dichlorophenoxyacetic acid (2,4-D)." Thesis, Durham University, 1989. http://etheses.dur.ac.uk/6325/.
Full textAbstract:
The aim of this work was to study the effect of the herbicide, 2,4-D on a mono- cot (Lolium temulentum Linn.) and a dicot (Raphanus sativus Linn.) in relation to drought stress, in order to elucidate if the combined treatments altered the survival of the plants. Herbicide effects were investigated on a number of plant developmental stages; germination, seedling growth, mature leaves and root function, and were combined with various water stress regimes.2,4-D did not alter the germination percentage in either species when applied singly or with polyethylene glycol (PEG) induce water stress. However, rate of seedling emergence and accumulation of chlorophyll, protein and proline were inhibited. Foliar application of 2,4-D at selective concentrations showed that in addition to induced growth distortion the herbicide reduced the survivial capacity of radish but enhanced that of rye grass to later drought stress. Analysis of the content of proline (a stress metabolite) in both species indicated that the accumulation of this compound was reduced in radish but enhanced in rye grass. In contrast, when 2,4-,VJ)&^Dlapplied via the roots, from water culture, the selectivity of effect was lost since proline accumulation was reduced in both species. Use of (^14)C-2,4-D showed that the herbicide remained in the roots when applied in water culture and that since a major response was seen in the roots this implied that some signalling was occuring between the two organs. From the results it would appear that the use of low doses of herbicides such as 2,4-D may be valuable in protecting certain plants from drought stress, whilst the susceptability of other plants could be increased hence making the herbicide more effective at low concentrations.
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Réthoré, Élise. "Integrative analysis of acquired thermotolerance in developmentally arrested Arabidopsis seedlings : Implication of energy metabolism." Thesis, Angers, 2019. http://www.theses.fr/2019ANGE0010.
Full textAbstract:
Dans le contexte du changement climatique, l’augmentation de la fréquence et de l’intensité des canicules a un impact négatif sur la physiologie des plantes, du fait de la perturbation structurale des protéines et des membranes par les fortes températures. Au cours de cette thèse, nous avons développé et caractérisé un système expérimental original dans lequel des plantules d’Arabidopsis thaliana sont arrêtées dans leur développement du fait d’une carence minérale. Ces plantules présentent une grande plasticité métabolique, notamment au niveau énergétique, qui leur permet de survivre pendant des semaines en état stationnaire. Nous avons ensuite réalisé une étude intégrative des processus qui permettent à ces plantules de survivre à un stress thermique normalement létal (43°C, 2 h), grâce à l’application d’un prétraitement à une température non létale (38°C, 2 h). Le pré-traitement à 38°C permet la protection du métabolisme énergétique ainsi que la reprise de la dynamique des organites lors de la phase de récupération. Au niveau transcriptionnel, les plantules pré-acclimatées surexpriment notamment des protéines chaperones et des gènes impliqués dans la photosynthèse et la régulation de l’expression des génomes mitochondriaux et plastidiaux. Au niveau protéique, l’accumulation d’HSPs et d’autres protéines de stress favorisent la récupération des plantules, tandis qu’en l’absence d’acclimatation, le choc thermique provoque la diminution des protéines ribosomales et l’accumulation de protéines impliquées dans la dégradation des protéines. Cette étude illustre l’intérêt de l’analyse multi-échelle pour décrypter les mécanismes de réponse des plantes aux stress<br>In the context of climate change, the increased frequency and intensity of heat waves will likely have a negative impact on plant physiology, due to the structural destabilization of proteins and membranes caused by high temperatures. As part of this thesis, we developed and characterized an original experimental setup in which Arabidopsis thaliana seedlings are arrested in their development because of mineral starvation. These seedlings exhibit a high metabolic plasticity, especially for energy metabolism, which allows them to survive in a steady state for weeks. Then, we performed an integrative analysis of the processes that allow these seedlings to survive an otherwise lethal heat stress (43°C, 2 h), thanks to a priming treatment at a nonlethal temperature (38°C, 2 h). Priming protects the energy metabolism and permits the recovery of organelle dynamics after stress. At the transcriptional level, primed seedlings overexpress many chaperone proteins and genes involved in photosynthesis, and in the regulation of the expression of mitochondrial and plastidial genomes. At the protein level, the accumulation of HSPs and other stress proteins favour seedling recovery, whereas in the absence of acclimation, heat shock provokes the decrease of ribosomal proteins and the accumulation of proteins implicated in protein degradation. This study highlights the relevance of multi-scale analysis to decipher mechanisms of stress response in plants
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Batlang, Utlwang. "Studies With Triazoles to Alleviate Drought Stress in GreenHouse-Grown Maize (Zea mays) Seedlings." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/33428.
Full textAbstract:
In semi-arid environments, dry-land farming often exposes crops to drought stress. Although some plant species are well adapted to drought, most crops are not. Drought can reduce plant populations and limit growth and development in ways that have serious yield consequences. Planting at the beginning of the wet season, when rainfalls are often sporadic and unreliable, can expose young maize seedlings to severe drought. Through the use of plant growth regulators (PGR), maize seedlings can perhaps be altered to elicit responses that mimic drought adaptation mechanisms. A series of studies conducted in the laboratory and greenhouse looked at the response of maize seedlings (two hybrids that differed in their reported drought sensitivity) to severe drought and to PGR applications with or without drought. Results showed that drought stress altered plant morphology and key physiological parameters. Applications of three triazoles (paclobutrazol, uniconazole and tetraconazole) altered morphology and physiology in ways that might impart drought resistance. Paclobutrazol and uniconazole increased root:shoot ratio in laboratory studies and in the greenhouse. When compared to non-triazole-treated controls, uniconazole and paclobutrazol treatments caused water conservation in earlier stages of drought stress, and therefore afforded increased transpiration (and presumably less stress) at later stages. Uniconazole and tetraconazole increased photosynthesis of well-watered plants. Proline content was increased to a greater degree by these same two triazoles under drought stress conditions. It is hoped that knowledge obtained from these studies can be extended to drought-prone areas where maize dry-land farming is practiced.<br>Master of Science
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Harrington, John T. "Physiological effects of moisture stress, moisture stress conditioning, and leaf area manipulations on black alder seedlings (Alnus glutinosa (L.) Gaertn.)." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/45674.
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<p>This project consisted of three studies, two of which
examined the effects of moisture deficits and moisture
stress conditioning of black alder seedlings and the third
examined the effects of shoot manipulations on the
physiology of black alder seedlings and the nitrogenase
activity of the seedlings' root nodules.</p>
<p>
Endophyte strain was found to be nonsignificant in
response to moisture deficit and moisture-stress
conditioning (MSC). Using regression analysis MSC
significantly decreased the impact of low water potentials
on photosynthesis and acetylene reduction. There were no
significant improvements in this response with increased
MSC periods. Exposure of nodules to dry soil conditions
while keeping the host plant hydrated did not significantly
reduce acetylene reduction, nodule sugar content,
transpiration or leaf conductance; however, photosynthesis
was significantly reduced. Only defoliations of 100%
significantly lowered acetylene reduction. Defoliations of
45% caused increases in photosynthesis and transpiration of
residual leaves three days following defoliation. Nodule
sugar content was unaffected by any level of defoliation.</p><br>Master of Science
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Bless, Yo-Neal. "Modulation of brassica rapa L. antioxidant activities by exogenous methylglyoxal under zirconium stress." University of the Western Cape, 2016. http://hdl.handle.net/11394/4961.
Full textAbstract:
>Magister Scientiae - MSc<br>With a decrease in water availability and arable land, and the ever-increasing reports of toxic chemical pollutants, it is crucial to elucidate plants’ mechanisms of adaptability to these abiotic stressors. South Africa alone accounts for approximately 30% of global Zirconium (Zr) production. However, reports on Zr-induced stress in plants are sparse. Increased mining activity leads to soil contamination which subsequently has harmful effects on crop plants. Under normal conditions B. rapa crop plants flourish, they are rapid in their cycling and circumvent the seed dormancy stage which enables them to have high yields over relatively short periods. However, when unfavourable conditions arise, such as exposure to toxic chemicals and metal ions like Zirconium, the development and growth of B. rapa L., much like other crop plants is affected. More specifically, the damaging effects of Zr is not only attributed directly; as with substitutions of biometals [like Iron (Fe)] in various biomolecules rendering them inactive, but more as a consequence of the production of toxic molecules such as reactive oxygen species (ROS) and methylglyoxal (MG). ROS such as superoxide anion (O₂⁻) and hydrogen peroxide (H₂O₂ ) are known to have signalling roles in plants with reports on their involvement in alleviating seed dormancy and seedling development. However, the signalling roles of MG are not known with regards to plant cells and have been reported more so in animal cells; playing vital roles in fat signalling in diseases such as diabetes. Furthermore MG, in plant and animal cells, directly converts oxygen (O₂) to O₂⁻ and thus increases the cell’s oxidative imbalance, leading to cell damage if O₂⁻ is not rapidly dismutated to H₂O₂ and H₂O by superoxide dismutase (SOD). In turn, H₂O₂ is more stable than O₂⁻ and consequently is more toxic to cells over time. Therefore, H O must be removed as well by a collection of enzymes, such as ascorbate peroxidase (APX) and catalases (CAT). In this study, possible stress-signalling of MG in seedlings under normal conditions and Zr-stress were investigated to establish whether MG at a low dose (6 μM) would benefit seedling growth and development, via a proposed preinduction of the B. rapa L. antioxidant system. Therefore, it was proposed that ROS accumulation due to the exogenous application of MG, would incite the activation of antioxidants and thus mitigate the effects of Zr stress. Physiological tests to determine dry weights (figure 3.2.3) and germination percentage (figure 3.2.2) revealed that MG-treated seedlings yielded an improved biomass and early development compared to Zr-treated seedlings and the control. Membrane damage as assessed by lipid peroxidation viz. Malondialdehyde [MDA] (figure 3.2.4) and conjugated dienes [CD] (figure 3.2.5) also indicated less damage in MG-treated seedlings compared to the Zr-treated set. The chlorophyll content observed was prominent (table 3.1). MG-treated seedlings exhibited a 40% and 15.5% increase compared to Zr-treated seedlings and the control respectively. Moreover cell viability had improved in MG-treated seedlings compared to the control, and in MG+Zr-treated seedlings only a slight increase in cell death occurred despite Zr being present. O₂⁻, H₂O₂ and •OH (figure 4.2.1 – 4.2.3) were investigated in B. rapa L. seedlings in response to Zr and MG by spectrophotometric biochemical assays, as well as their scavenging enzymes, MG accumulation and Gly-I activity. Furthermore, BrGLY1 gene expression and Zr-uptake by ICP-OES were performed. Seedlings treated with MG and Zr respectively showed an increase in ROS. However, all of the ROS observed in MG+Zr-treated seedlings were markedly lower compared to Zr-treated seedlings. SOD and CAT activity observed in MG+Zr-treated seedlings had decreased compared to Zr-treated seedlings, whereas APX activity had increased. Gly-I activity and BrGlyI gene expression had increased across all treatments, showing an elicited response to oxidative stress, due to the observed upregulation, as a result of the accumulated MG. The observed Zr-uptake in MG+Zr-treated seedlings was inhibited by 5-fold compared to Zr-treated seedlings. Clear signs of stress were evident in seedlings treated with Zr compared to the control and MG- treated seedlings, the MG-supplemented (MG and MG+Zr) seedlings displayed a vast improvement comparatively. Modulation of antioxidant activity observed in this study is indicative of an incited response to oxidative stress (figure 4.2.4 – 4.2.6). MG revealed distinct involvement in stress-signalling, ROS levels had increased, although not as severely as with Zr-treated seedlings, but seemingly enough to activate antioxidants without eliciting damage. Furthermore, the proposed early-onset activation of antioxidants has been observed in B. rapa L. seedlings of this study, and as such has resulted in improved growth, development and seed germination. The results of this study has therefore negated the previous reports on MG-toxicity (at high concentrations), and has shed light on further properties of this ubiquitous and inevitably-occurring metabolite at low levels.<br>National Research Foundation (NRF)
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Baloglu, Mehmet Cengiz. "Expression Analysis Of Nac Type Transcription Factors On Wheat Seedlings Under Abiotic Stress Conditions." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613501/index.pdf.
Full textAbstract:
Wheat is the most important grain crop grown in our country providing greatest part of the daily nutritional requirement. Abiotic factors including salinity, drought, cold and heat stresses affect quality and yield of wheat varieties used for the production of both bread and pasta flour.
NAC proteins form one of the widest families of plant specific transcription factors. Members of this family are related with development, defense and abiotic stress responses. TaNAC69-1 and TtNAM-B2 genes were isolated from T.aestivum and T.turgidum, respectively. Then they were cloned into different monocot and dicot expression vectors to be used for further wheat and tobacco genetic transformation studies. To understand effects of salinity, drought, cold and heat stresses on expression profiles of TaNAC69-1 and TtNAM-B2 genes, quantitative real time PCR was performed. The time series expression profiles of TaNAC69-1 show that it was signi
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Hendricks, Kaylin. "Signalling molecule “calcium” improves germination and growth of Sorghum bicolor seedlings under salt stress." University of the Western Cape, 2021. http://hdl.handle.net/11394/8254.
Full textAbstract:
>Magister Scientiae - MSc<br>Abiotic stress, mainly in the form of extreme temperatures, drought and salinity has caused major crop losses worldwide, putting a severe strain on agriculture. Salinity severely limits plant growth and productivity and affects all aspects of the plant’s development including the most crucial stage; germination. This study investigated the effect of salt (NaCl) stress on Sorghum bicolor seedlings and the role of exogenously applied calcium (Ca2+) to ameliorate the effects of salt stress during germination. Sorghum seeds were germinated in the presence and absence of various NaCl (100, 200 and 300 mM) and Ca2+ (5, 15 and 35 mM) concentrations. Several assays including physiological (germination and growth assays), biochemical (osmolytes and oxidative stress markers), anatomical (epidermal and xylem layers) and expression profiles of key genes [antioxidant (SbSOD, SbAPX2 and SbCAT3), Salt Overly Sensitive (SbSOS1, 2 and 3) pathway enzymes and the vacuolar Na+/H+ exchanger antiporter2 (SbNHX2)] were investigated. Salt stress delayed germination and negatively affected growth as observed by the reduced root and shoot length and decreased fresh and dry weight. There was an increase in proline content and oxidative stress markers (H2O2 and MDA) under salt stress. Oxidative stress resulted in damage to the epidermal and xylem layers as observed on Scanning Electron Microscopy (SEM) images. Quantitative real-time polymerase chain reaction revealed that salt stress
induced the expression of SbAPX2, SbCAT3 and SbSOS1 genes, whereas SbSOD4A, SbSOS2, SbSOS3 and SbNHX2 genes were not affected by salt. Exogenous application of Ca2+ counteracted the harmful effects of salt stress by improving germination efficiency, promoting seedling growth, reducing oxidative damage and the Na+/K+ ratio, indicating the protective effect. Ca2+ also effectively protected the epidermis and xylem layers from the severe damage caused by salt stress. In the presence of Ca2+ the expression of SbAPX2 and SbCAT3 was reduced except for the SbNHX2 gene, which increased by 65-fold compared to the control. The results obtained suggests that sorghum is able to respond to salt stress by inducing osmolytes, the antioxidant defence system as well as the SOS pathway. Furthermore, 5 mM Ca2+ was determined as the optimum Ca2+ concentration required to enhance sorghum’s tolerance to salt stress.
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Rayan, Ahmed Mohamed. "The elucidation of the pathway of water movement in barley (Hordeum vulgare L.) seedlings using anatomical, cytological and physiological approaches." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184785.
Full textAbstract:
Leaves of young barley (Hordeum vulgare cv Arivat) seedlings were examined anatomically, physiologically and cytologically to infer the pathway of transpirational water movement and to understand the basis for the selective responsiveness of the growing region to osmotic stress. Vessels with open lumens were found to extend from the intercalary meristem to the expanded blade, and all vessels are present in 5 functional vascular bundles (FVB) which are separated by 20 to 30 closely packed mesophyll cells and 2 to 3 immature vascular bundles (IVB). Heat pulse transport data confirmed the anatomical suggestion that water will move throughout the leaf in open vessels and they showed also that osmotic stress will reduce water transport within 1 min, which is before transpiration is lowered. Water representing about 2 per cent of the total tissue water was obtained by centrifuging cut sections of the growing region at 5 X g against an adsorptive surface. This water is probably xylem plus cell wall water because it is easily removed, its volume is 2X that calculated to be in the vessels, and it exchanges more readily with the water in the nutrient solution than the bulk tissue water. This lack of free exchange indicates apoplastic water is somewhat separated from mesophyll cells, and it is hypothesized that osmotic stress causes sudden growth cessation and initation of metabolic changes because (a) reduced water availability together with ongoing transpiration will cause a sudden reduction in the xylem's water potential, (b) there is a lateral transmission of this reduced water potential through walls of all cells in the growing region, and (c) cells can respond in some way to changes in water potential around them. Most cells in the expanded blade are considered unresponsive to osmotic stress because transpirational water will move predominantly from the 5 FVB through the closest stomata, so only cells closest to those bundles will be altered rapidly by stress.
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Löf, Magnus. "Environmental stress on establishment and growth in Fagus sylvatica L. and Quercus robur L. seedlings /." Alnarp : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5625-8.pdf.
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Akel, Saleh Ali Al 1963. "Water stress-induced osmotic adjustment in expanding leaves of tepary bean (Phaseolus actifolius Gray) seedlings." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/278372.
Full textAbstract:
Tepary (Phaseolus actifolius Gray) beans perform better than common beans (Phaseolus vulgaris) under drought conditions. The mechanism of drought tolerance in tepary bean seedlings was explored by determining the water potential (WP), osmotic potential (OP), relative water content (RWC), free sugar concentration, and the level of K ion within the expanding leaves. Two week old tepary bean seedlings were subjected to a gradual water stress with sorbitol solutions exhibiting OP values of -0.19 MPa and -0.47 MPa. Turgor remained constant whereas WP, OP and RWC declined following the stress treatment. Osmotic adjustment (OA) occurred in each treatment but the contribution of sucrose and fructose was minor. Some sorbitol was translocated to leaves and contributed to OA. The decrease of K ions in leaves indicated that these ions did not contribute to the OA. A significant decrease in cell size was observed as determined by decrease in TW/DW ratio.
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Al-Akel, Saleh, and Paul G. Bartels. "Water Stress-Induced Osmotic Adjustment in Expanding Leaves of Tepary Bean )Phaseolus actifolins, Gray) Seedlings." College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221443.
Full textAbstract:
Tepary beans perform better than common beans under drought conditions. The mechanism of drought tolerance in tepary bean seedlings was explored by determining the water potential, osmotic potentia4 relative water content and level of free sugars and concentration of K ions within expanding leaves. Two week old seedlings were subjected to a gradual water stress with sorbitol solutions exhibiting OP values of -0.19 MPa and -0.47 MPa. Tugor remained constant whereas WP, OP and RWC declined following the stress treatment. Osmotic adjustment (0.4) occurred in each treatment but the contribution of sucrose and fructose to OA was minor. Some sorbitol was translocated to leaves and contributed to OA. The K ions did not contribute to the OA. A significant decrease in cell size was observed
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Ercan, Oya. "Effect Of Drought And Salt Stresses On Antioxidant Defense System And Physiology Of Lentil (lens Culinaris M.) Seedlings." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609250/index.pdf.
Full textAbstract:
In this study, 14 days old lentil seedlings (Lens culinaris Medik cv. Sultan), which were subjected to 7 days of drought (20% PEG 6000), and salt (150 mM NaCl ) stress , were examined in a comparative manner for the effects of drought and salt stress treatments. In shoot and root tissues physiological parameters such as wet-dry weight, relative water content, root-shoot lengths, membrane electrolyte leakage, and lipid peroxidation in terms of malondialdehyde (MDA) were determined. H2O2 content, proline accumulation and chlorophyll fluorescence analysis were also performed. Changes in the activity of antioxidant enzymes such as superoxide dismutase (SOD: EC 1.15.1.1), catalase (CAT: EC 1.11.1.6) ascorbate peroxidase (APX: EC 1.11.1.11) and glutathione reductase (GR: EC 1.6.4.2) were observed upon stress treatments. In salt treated lentil seedlings, significant decreases in wet-dry weight, RWC, shoot-root length and chlorophyll fluorescence measurements indicated a sensitivity, when compared to drought treated plants. Higher MDA concentration and higher electrolyte leakage amounts are supported these results. APX, GR and proline seem to play important roles in antioxidant defense against salt stress for both tissues by removing reactive oxygen species and protecting macromolecules and membranes. GR and proline are also maintains the main protective mechanism against drought stress effects. SOD is active in drought stressed roots and salt stressed shoots, where the H2O2 contents are also observed to be increased.
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Phang, Ing Chia. "Response of Arabidopsis thaliana seedlings to lead exposure." Thesis, University of Canterbury. School of Biological Sciences, 2010. http://hdl.handle.net/10092/4467.
Full textAbstract:
Lead (Pb) is one of the most commonly occurring, highly persistent and widely distributed heavy metal contaminants in the environment. It has a tendency to bioaccumulate in animals and plants, and potentially, it is able to enter the human food chain where it poses a hazard to public health. Generally, conventional remediation technologies applied to decontaminate heavy metals from groundwater and soils are very costly. Hence, phytoremediation has emerged as an ecologically friendly and economically attractive technology that uses green plants to clean up heavy metal contaminated sites. However, a lack of knowledge of the biological processes associated with plant responses to Pb (e.g. Pb uptake, accumulation, translocation, and tolerance) has been a bottleneck for the application of Pb phytoremediation in the field. A model genetic system of higher plants, Arabidopsis thaliana, was selected to further examine the physiological, biochemical and molecular events occuring in plants under Pb stress.
The overall aim of this project was to obtain a better understanding of plant responses to Pb contaminants in the early developmental stages of A. thaliana seedlings. This research encompassed the physiological responses of A. thaliana seedlings to Pb exposure, monitoring their antioxidative defence systems, and investigating the participation of annexin 1 in the response to Pb-mediated oxidative stress. This research also assessed the protective effect of nitric oxide on Pb-induced toxicity of A. thaliana seedlings and it isolated a putative Pb tolerant mutant from an EMS-mutagenized M2 population. A multiexperimental approach was adopted to achieve these objectives.
A. thaliana seedlings were grown on modified Huang & Cunningham (1996) nutrient solution containing 0.8% (w/v) agar, with and without Pb(NO3)2, under controlled conditions. A. thaliana seedlings were insensitive to Pb during seed germination. In treatments with up to 200 μM Pb(NO₃)₂, morphological changes and inhibition of root growth were observed in the 7-d-old seedlings. A tolerance index revealed that Pb(NO₃)₂ concentration of 75 μM and higher brought about more than 50% root growth inhibition. Pb was predominantly retained in the roots. Analysis using a graphite furnace atomic absorption spectroscopy indicated that the level of Pb accumulation in A. thaliana roots was greatly dependent on the Pb(NO₃)₂ concentrations, but only a small fraction of the accumulated Pb was translocated to the shoots (18 - 43%). Transmission electron microscopy analysis showed that Pb was mainly immobilized in the cell walls and intercellular spaces. This was interpreted as a mechanism that minimizes the entry of Pb into cells and interference with cellular functions. Pb that gained entry into the cytoplasm was sequestered into the vacuoles.
The toxicity of Pb in the cytosol of A. thaliana seedlings was studied by measuring the H₂O₂ and lipid hydroperoxide levels using a microplate reader. When the Pb(NO₃)₂ concentration in the growth medium was 100 μM, the 7-d-old seedlings contained 2.2-fold higher H₂O₂ and 9.6-fold higher lipid hydroperoxide than the control without Pb(NO₃)₂. This was followed by an up-regulation of the activity of antioxidative enzymes, including superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPX), and general peroxidase (POD) by 2.1-, 3.2-, 2.3-, 1.8- and 4.6-fold, respectively, compared with the control. Pb toxicity is known to trigger oxidative stress, but A. thaliana seedlings appeared to be capable of activating cell rescue, defending themselves against harmful oxidative stress and also acclimating to Pb. Data from physiological and biochemical analysis indicate that a combination of avoidance and tolerance mechanisms exists in Pb-treated A. thaliana seedlings to maintain the essential cellular metabolism for survival.
Real-time reverse-transcription polymerase chain reaction was used to show the involvement of AnnAt1 in the response of 7-d-old A. thaliana seedlings to a high threshold concentration of Pb. When the seedlings were treated with 100 μM Pb(NO₃)₂, AnnAt1 message levels were up-regulated by 2.12-fold. Pb-mediated oxidative stress may be a component of AnnAt1 gene expression. AnnAt1 potentially could be invoked to reduce the toxic effects of Pb stress by acting as ROS and/or Ca²⁺ signals, as a membrane protector, in detoxification of excessive ROS, or in sequestration of Pb.
Pb stress symptoms were less evident in seedlings pre-treated with 1 mM sodium nitroprusside (SNP), a nitric oxide (NO) donor. The present study found that exogenous NO did not alter Pb transport into the plants or efflux pumping of Pb at the plasma membrane. However, NO conferred protection to 7-d-old A. thaliana seedlings primarily by acting as an antioxidant or a signal for actions to scavenge excessive ROS level. The application of exogenous NO before subjecting to 100 μM Pb(NO₃)₂ decreased H₂O₂ back to its original level, and reduced 50% lipid hydroperoxide in the Pb-treated seedlings. As a result, the antioxidative enzyme activities in Pb-exposed seedlings pre-treated with SNP were 23 - 45% lower than those without SNP pre-treatment. Less antioxidative enzyme activities were probably needed to counteract the reduced amount of Pb-induced ROS in A. thaliana seedlings.
A post-germination procedure involving prolonged exposure to 150 μM Pb(NO₃)₂ was developed to screen an EMS-mutagenized M2 population of A. thaliana. Potential Pb tolerant mutants were selected based on the ability to grow with their roots penetrating into the medium and maintain purple-green leaves without wilting. A minority of the survivors appeared to go into a resting stage and they seemed to have altered transporters that prevented Pb from entering the cells. Only one putative Pb mutant (M3-1) was recovered from the rescue and set seeds. The M₄ generation of this putative Pb mutant was re-screened for phenotypic confirmation and to determine the regulation of AnnAt1. The 7-d-old putative Pb mutant seemed to display enhanced root and shoot growth in the presence of 150 μM Pb(NO₃)₂ compared to the wild-type seedlings. The transcript level of AnnAt1 in this putative Pb tolerant mutant increased by 2.19-fold when exposed to 150 μM Pb(NO₃)₂.
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Borsos-Matovina, Vera. "The effect of Ambiol on growth and stress tolerance of Pinus banksiana and Picea mariana seedlings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0007/MQ29456.pdf.
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Cheng, Chen. "Semi-global Analysis of the Early Cold Stress Response Transcriptome of Developing Seedlings of Rice (Oryzasativa L.,japonica)." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/ChengC2006.pdf.
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Bueno, Garcia Betty Andrea [Verfasser]. "Competition for nitrogen between native woody seedlings and invasive plants under abiotic stress / Betty Andrea Bueno Garcia." Konstanz : KOPS Universität Konstanz, 2019. http://d-nb.info/1220634336/34.
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Aksoy, Emre. "Effect Of Drought And Salt Stresses On The Gene Expression Levels Of Antioxidant Enzymes In Lentil (lens Culinaris M.) Seedlings." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609960/index.pdf.
Full textAbstract:
This study was carried out for understanding of antioxidant mechanisms of lentil under abiotic stress conditions. For this aim, 14 days old lentil seedlings (Lens culinaris Medik cv. Sultan-1) were subjected to drought (20% PEG 6000), and salt (150 mM NaCl ) stress for 6, 12 and 24 hours, for 3, 5 and 7 days. PCR conditions for Mn SOD, Cu/Zn SOD, chloroplastic/mitochondrial GR, CAT and chloroplast /stromal APX antioxidant enzymes were optimized. Then, total RNA was isolated from stressed and non-stressed plant roots and shoots. The gene expression levels of Mn SOD and Cu/Zn SOD were examined by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) technique. Arabidopsis 18S rRNA was used as internal control in multiplex PCR technique. Relative expression levels of Mn SOD were lower in shoots and roots under salt stress while no significant change was obtained under drought conditions in both tissues. Relative expression levels of Mn SOD were increased on 5th day of salt and drought applications in both shoots and roots. Relative expression levels of Cu/Zn SOD increased after 5th, and on 1st and 7th days of drough treatment in shoots and roots, respectively. On the other hand, expression levels of Cu/Zn SOD increased on 3rd and 5th days of salt treatment in shoot tissues. Although it is nearly impossible to understand the whole antioxidant mechanism of plants under environmental stresses, this study was the first step to learn about molecular background of antioxidant defence mechanisms in lentil.
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Tseng, Elizabeth Chang-Hsu. "The impact of ozone, water stress, and acid rain on the growth and physiology of fraser fir seedlings." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/77734.
Full textAbstract:
Three studies were conducted to determine the effects of ozone, water stress, and simulated acidic rain on the growth and physiology of Fraser fir seedlings. In Experiment I, seedlings were first exposed to 2 levels of moisture stress conditioning (MSC) for four weeks, and 3 levels of ozone ( < 0.02, 0.05, and 0.10 ppm) and three levels of water stress (control, moderate, and severe) for 10 wks. The 2 MSC levels were a control (well-watered at all times) and a stress treatment in which seedlings were not watered until pre-dawn needle water potential measurements ('I') fell below -1.0 MPa. The 3 levels of water stress were a control (well-watered at all times); a moderately stressed treatment (seedlings watered when 'I' levels fell between -0.8 and -1.0 MPa); and a severely stressed treatment (seedlings watered when 'I' fell below -1.2 MPa). Fraser fir seedlings were exposed to 3 levels of simulated rain (pH 3.0, 4.3, and 5.6) and 2 levels of ozone ( < 0.02 and 0.10 ppm) in Experiment II for 10 wks. Fraser fir seedlings in Experiment III were exposed to ozone levels of < 0.02, 0.05, and 0.10 ppm ozone and control, moderate, and severe water stress (as specified above) for 10 wks during the first year. Seedlings were then exposed to 2 levels of ozone ( < 0.02 and 0.10 ppm) for 10 wks in the following year. Analysis of data indicate that ozone of 0.10 ppm significantly decreased net photosynthesis (Pn) in one study but was not significant in reducing Pn in the other two studies. Ozone also failed to reduce growth significantly; however, decreasing trends were often apparent. Fraser fir biomass, transpiration (Ts), and needle conductance (Cs) were significantly decreased by water stress. Water-use efficiency was also improved as a result of prior moisture stress. Simulated acidic rain did not result in any significant changes in biomass accumulation, height, or diameter increment over the ten week period of the study. A solution of pH 3.0 did result in significantly higher root surface area and significantly reduced Ts after 5 wks of exposure; these responses are possibly due to a fertilization effect. No treatment interactions were significant. However, the combined, cumulative effect of all of these stresses may contribute to an overall decline in forest ecosystem productivity.<br>Master of Science
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Sarmiento, Aneth [Verfasser]. "Evaluation of the plastidic antioxidant system in Jatropha curcas and Swietenia macrophylla seedlings submitted to drought stress / Aneth Sarmiento." Berlin : Freie Universität Berlin, 2018. http://d-nb.info/1196802920/34.
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Costanzo, Nadine. "The effects of stress on biomass, soluble sugar concentrations and VA mycorrhizal colonization in sugar maple seedlings (Acer saccharum Marsh.)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ43632.pdf.
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Boyoglu, Seyhan. "Characterization Of Glutathione S-transferase Activity In Turkish Red Pine (pinus Brutia, Ten.): Variation In Environmentally Cold Stressed Seedlings." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604759/index.pdf.
Full textAbstract:
Plants can not escape from biotic and abiotic stress factors such as, extreme temperatures, high light intensity, drought, UV radiation, heavy metals, and pathogen attack. Plants have versatile defens systems against such stress conditions. In this study, the role of glutathione S-transferases (GSTs) in cold stress conditions were examined. Glutathione S-transferases are the enzymes that detoxify natural and exogenous toxic compounds by conjugation with glutathione. Glutathione, an endogenous tripeptide, is important as reducing agent, nucleophilic scavenger, and alleviate the chemical toxicity in the plants by the reaction of GSTs. Glutathione conjugates can be transported to the vacuoles or apoplast and are generally much less
toxic than the parent compounds. In plants there are four distinct families of the soluble GSTs, namely Phi (F), Type I<br>Zeta (Z), Type II<br>Tau (U), Type III<br>Theta (T), Type IV. By contrast with the mammalian families of GST, relatively little is known about the plant GST families. Up to date, there is not any study on GST isolation and characterization from Turkish red pine, in this respect, this study well play a frontier role the future research dealing with this topic.
In this study, some properties of Turkish red pine GST activity towards CDNB (1-chloro-2,4 dinitrobenzene) were examined. The average specific activity of Turkish red pine GST towards CDNB was found as 200±<br>50 (Mean±<br>SE, n= 18) nmole/min/mg cytosolic protein. GSTs in cytosol prepared from Turkish red pine needles retained its activity without loss for four weeks at -80&<br>#61616<br>C. The rate of conjugation reactions were linear up to 0.8mg of Turkish red pine cytosolic protein and 0.4 mg cytosolic protein was routinely used. The Turkish red pine GST showed its maximum activity at pH 8.0 in 25 mM phosphate buffer and 42 &<br>#730<br>C. The measurements were carried out at room temperature (RT) of 25 &<br>#61616<br>C. Turkish red pine GST seemed to be saturated at 1 mM CDNB and 1 mM GSH concentrations. The Vmax and Km values of Turkish red pine GST for CDNB was 416nmole/min/mg protein and 0,8 mM, respectively, and for GSH 106.4 nmole/min/mg protein and 0.10 mM, respectively. Turkish red pine cytosol was applied on DEAE-Sepharose fast flow column but almost no purification was achieved with respect GST activity. In order to examine the effects of cold stress on Turkish red pine GST activity, the GST activity was determined in 240 seedlings at &ndash<br>3&<br>#61616<br>, 0&<br>#61616<br>and 13 &<br>#61616<br>C environmental temperatures. It was observed that GST activity was the highest at -3&<br>#730<br>C and the lowest at 13&<br>#730<br>C in both cold resistant and sensitive families with the exception of Yaylaalan and Ç<br>ameli.
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Magoba, Rozwivhona Faith. "Influences of river flows on recruitment success of Fynbos riparian vegetation along selected high gradient streams in the Western Cape, South Africa." University of the Western Cape, 2014. http://hdl.handle.net/11394/4362.
Full textAbstract:
>Magister Scientiae - MSc<br>Riparian vegetation occurs in two distinct zones, the wet bank and the dry bank. Knowledge on how the flow regime influences the zonal structure of riparian vegetation is required to mitigate the adverse effects of water resource utilization on riparian vegetation. The first objective of this study was to determine whether flow exerts a physical influence on zonal structure pre- or post-recruitment. An examination of the survival of seedlings and saplings was conducted along Western Cape rivers to investigate seedling persistence and survival on lateral zones. A comparison of the ratios of seedlings, saplings and adults in different riparian zones for the years, 2004, 2011 and 2013, was carried out. The results suggest that in general seeds are deposited randomly on the banks, where they germinate and become seedlings. Seedlings that become established at locations unsuitable for their persistence into adulthood are removed either by high flows or perish during dry conditions. Thus, lateral zonation eventually develops due to species differences in tolerance to conditions at different positions on the banks. The second objective was to explore the effects of the reduction in dry season low flows on the recruitment success of riparian species at sites upstream and downstream of abstraction points. At most sites plants were arranged into different lateral zones and the numbers of species between upstream and downstream sites were not significantly different. There were significant differences in the abundances between up- and downstream sites, with the loss of herbaceous plants and sedges at downstream sites, both of which favour moist conditions. Also, in the absence of dry season flows, the seedlings of dry bank tree species recruited closer to the channel than those at the sites with summer flows. The shifting of the dry bank into the channel narrows the channel, which may affect the hydraulic pressures exerted during floods. The spatial arrangement in the riparian zone has as much to do with flow conditions post recruitment as it does with conditions during recruitment. This shows that the structure of riparian plants is determined not only by whether or not the minimum flows are met, this points to the need to reinstate the naturally variable flow and adopting a holistic approach for the understanding and management of aquatic systems.
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Li, Shen-En, and 李慎恩. "Effects of High Temperature Stress on the Growth of Wheat Seedling." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/j6vbk2.
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碩士<br>國立中興大學<br>農藝學系所<br>106<br>Wheat (Triricum aestivum) is one of top three food crops in the world, it is a temperate crop and the cultivation period is in autumn in Taiwan. Due to climate change, the temperature during wheat sowing period is continuously elevated. Study on the effects of high temperature stress on wheat seedling become an important issue. We focus on the wheat growth and physiological responses to high temperature stress from germination to seedling in this thesis. We use a Taiwan cultivar: Taichung selection 2 (TCS 2) for material, maintaining growing temperature at 30 or 35℃ as high temperature stress, and 25℃ as controlled temperature. Results show that 35℃ high temperature stress doesn’t affect wheat germination percentage, but slow down germination rate, and, significantly inhibit growth of shoot and root, causing significant reduction of fresh weight, dry weight, height and root length. Although high temperature stress elevates chlorophyll content, the decreased chlorophyll a/b, Fv/Fm ratio and no significant change in the shoot soluble carbohydrate and starch content show that there might be functional damage in wheat chlorophyll under high temperature stress. In addition, high temperature stress causes increased protein content and less reduction in protease specific activity, SDS-PAGE show that high temperature stress makes some bands thicker. We also find out high temperature stress induce the occurrence of drought stress and oxidative stress, causing the reduction of the shoot relative water content, soil water content and the elevation of proline content, and causing damage to the membrane from accumulation of H2O2 and MDA content. When we analysis its antioxiditive system, we find that high temperature stress elevates antioxidative enzyme activity. Furthermore, analysis of 11 days old seedling shows that 35℃ high temperature stress has more serious inhibition in growth of new leaf than the rest of seedling part. Compared with controlled temperature, 30℃ is the tolerant high temperature stress for wheat TCS 2, accelerating its seedling growth.
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Stjernberg, Ernst I. "The effectiveness of reflective tarpaulins in protecting tree seedling against heat stress." Thesis, 1995. http://hdl.handle.net/2429/3664.
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Reflective tarpaulins are used extensively in western Canada to protect tree seedlings against
solar radiation during on-site storage and transportation. This project determined heat transfer
characteristics of new and used reflective tarpaulins, and a FIST (Fiberglass Insulated Seedling
Transporter) canopy. Containerized white spruce (Picea glauca (Moench) Voss) seedlings in
shipping boxes were stored under tarpaulins and in the FIST canopy for up to six days in June,
1992. An unprotected seedling box was used as the control. Average seedling box temperatures
per each 15-minute period were recorded for 144 h. Solar irradiance and wind speed at the test
site were recorded simultaneously with box temperatures. The electrical conductivity of needles
was measured after storage. Seedlings were withdrawn daily for six days and outplanted in a
nursery plot in a split-plot randomized complete block design with repeated measurements
within each experimental unit. Root collar diameter, total height and survival were recorded for
three growing seasons. Samples of the tarpaulins were also tested under controlled conditions
for ability to resist heat transfer.
Seedling box temperatures ranged up to 35°C. Significant differences in 144-hour heat sums
were found between: new and used tarpaulins; various used tarpaulins; tarpaulins and control;
three new tarpaulins and the FIST canopy. Relative conductivities indicated no storage-induced
damage to cell membranes. Survival after three years was 99.8%. Significant differences in
growth were found but were more likely related to differences in soil nutrient differences within
the plot. Storage temperature and length had no effect on growth and survival.
A laboratory experiment tested for storage-induced pre-conditioning effects. Controls and
seedlings pre-conditioned 4 and 8 days for 3 h at 30°C, were heat stressed for 8 h or 48 h at 30,
35, and 40°C. Electrical conductivities of needles were measured. Seedlings were outplanted in
two plots with a completely randomized design. Root collar diameter, total height and survival
were recorded for two growing seasons.
No cell membrane damage was observed. Survival after two years was 99.5%. Evidence for a
pre-conditioning effect is inconclusive. The 8-day pre-conditioning may have resulted in higher
growth in seedlings heat stressed for 48 h.
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Wei, Mi-Yin, and 韋宓妍. "Studies on NaCl stress of rice seedling roots: the role of hydrogen peroxide." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/45778341216399067074.
Full textAbstract:
碩士<br>國立臺灣大學<br>農藝學研究所<br>100<br>In this thesis, rice (Oryza sativa L. cv. Taichung Native 1) etiolated seedlings were used to investigate (a) the role of H2O2 in NaCl-inibited growth of rice etiolated seedling roots, (b) the role of H2O2 in NaCl-increased glutathione reductase(GR)activity of rice etiolated seedling roots, (c) and the role of H2O2 in NaCl-increased heme oxygenase activity of rice etiolated seedling roots.
Rice etiolated seedlings treated with NaCl increased H2O2 production in rice roots (3 hours), and then inhibited root growth of etiolated seedlings (6 hours). Addition of H2O2 scavenger ascorbic acid (AsA) and nitric oxide (NO) donor sodium nitroprusside(SNP) , which decreased H2O2 accumulation, could not reduce NaCl-inhibited growth in rice roots. Also, application of NADPH oxidase inhibitors diphenyleneiodonium(DPI) and imidazole(IMD), which inhibited the H2O2 production, had no effect on NaCl-inhibited root growth. These data indicated that H2O2 production through NADPH oxidase caused by Na+ is unlikely responsible for
NaCl-inhibited root growth.
NaCl treatment increased H2O2 production and GR activity in rice roots. Addition of AsA and SNP, which decreased H2O2 accumulation, could lower the NaCl-induced GR activity. Also, application of DPI and IMD, which inhibited the
H2O2 production, reduced the NaCl-induced GR activity. NaCl treatment resulted in an increase in HO activity in roots of rice etiolated seedlings. Results of time-course study indicated that H2O2 accumulation occurred 3 hours after NaCl treatment, whereas the increase in HO activity occurred 6 hours after NaCl treatment. Addition of AsA and SNP, which decreased H2O2 accumulation, could lower the NaCl-induced
HO activity in rice etiolated seedling roots. Also, application of DPI and IMD reduced the NaCl-induced HO activity. Moreover, NaNO3 and NaCl are equally effective in
inducing GR and HO activity, indicating that Na+ but not Cl- is responsible for increasing GR and HO activities.
Based on the data of this thesis, it is concluded that H2O2 production caused by NaCl may be responsible for NaCl-increased GR and HO activities in rice etiolated seedling roots.
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Yu, Sung-Han, and 游松翰. "The Rice Transcription Factor, OsbHLH046, Contributes to Salt Stress Tolerance at Seedling Stage." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/21262582719596674378.
Full textAbstract:
碩士<br>國立臺灣大學<br>農藝學研究所<br>104<br>Rice basic-Helix-Loop-Helix (OsbHLH) transcription factors (TFs) belong to a multiple gene family and are known to involve in rice growth, development, regulating abiotic stress-responsive gene expression and tolerance of rice. However, because functional redundancy within the super gene family and the pleiotropic effect of individual TF, the specific function for corresponding OsbHLH is not easy to be determined. In this study, we identified an OsbHLH046 TF which is down-regulated by salt and cold treatments from previous microarray result and further confirmed the gene expression by reverse transcription-PCR (RT-PCR). The OsbHLH046-GFP fusion protein showed OsbHLH046 is located in nucleus. Based on the predication of rice eFP browser and the GUS-histochemical staining indicated that OsbHLH046 is expressed in the embryo, seedling root, lateral roots, shoots and anthers. The gene expression was higher at the early germination stage then declined to lower level within 3rd leaf stage. Compared with WT, the Osbhlh046, a Tos17 knocked-down rice mutant, displayed late seed germination, growth retardation, and unable to recover from salt stress at seedling stage. The q-PCR data indicated that salt tolerance related genes in such as OsABI5, OsNHX2 were differential expressed between two plants during recovery stage. The MDA was overaccumulated in Osbhlh046 mutant compared to wild type after recover from salt stress. The ICP-OES elemental analysis also revealed that the Osbhlh046 plant have lower K+ content level, which may not able to maintain the Na+ homeostasis. Meanwhile, the callus of OsbHLH046 overexpression line showed a relative poor regeneration rate. Taken together, these results suggested that OsbHLH046 plays as a positive regulator in seed germination, seedling growth, and contributes to the ability of rice to recover from salt stress.