Academic literature on the topic 'Plant physiology – Experiments'

Bioretention facilities have been widely used in the construction of Sponge City in China, but there have also been doubts about whether road runoff pollutants have adverse effects on plant growth. In response to this problem, this paper explored the effects of bioretention on the removal of pollutants and explored the effects of runoff on plant growth and physiology. The results showed that (1) the average concentration reduction rate and load removal rate of TN and NO3--N were above 70%, the average NH4+-N concentration reduction rate and load removal rate were greater than 90%, and the removal of elemental N was affected by the influent concentration. The removal effect of the four heavy metals was not very great. The average concentration reduction rate and load removal rate of heavy metals were 65.4–95.7% and 85.4–99.4%, respectively. The cumulative load removal rate of various pollutants was above 87.0%. (2) The runoff of high–concentration pollutants had a negative or no significant effects on the net photosynthesis rates (Pn), chlorophyll contents (CC), and electrolyte leakage (EL) of most plants (e.g., Iris tectorum Maxim, Rosa xanthina Lindl, and Ligustrum vicaryi). It had a significantly negative effect on the plant height of shrub plants (e.g., Rosa xanthina Lindl and Ligustrum vicaryi), but had a positive effect on Pn and CC of Iris lactea var. chinensis. (3) The runoff of low–concentration pollutants had a positive or no significant effects on the physiological indexes of herbaceous plants (e.g., Iris tectorum Maxim and Iris lactea var. chinensis), but there were no explicit conclusions regarding the physiological indicators of shrub plants (e.g., Rosa xanthina Lindl and Ligustrum vicaryi). It had no obvious effects on the plant height of these four species of plants.

The principles of plant physiology are best learned in an environment where students are directly engaged in the process of scientific inquiry. Working from this assumption, we have developed a two-stage approach to laboratory instruction that fosters student-directed research within an undergraduate plant physiology course. During the first 10 weeks of a 16-week semester, students develop competency in measuring physiological variables by using an array of standard analytical techniques. A core set of 10 laboratory experiments provides structured instruction and teaches the principles of modern physiological analyses. During week 11, students observe a demonstration of a plant response, where the underlying cause of the phenomenon is not evident. Working together in groups of three or four, students hypothesize on the physiological mechanisms that may be involved. After submitting a statement of hypothesis and a plan of study, each group then requests the necessary instrumentation, plant material and greenhouse and/or growth chamber space to conduct their experiments. Results of their experimentation are presented during week 15 in both written and oral formats. The approach appears to help students to integrate and connect learnings from earlier in the semester to solve a defined problem. Further, students learn how to judge the reliability of experimental results and to evaluate whether conclusions drawn are justified by the data.

Field experiments were conducted in two seasons to investigate growth, physiology and yield responses of cabbage (Brassica oleracea L. cvs Pennant and Rio Grande) to deficit irrigation. In 2012 season, 50% of crop evapotranspiration (ETc) irrigation temporarily decreased plant size, reduced leaf area, fresh weight, relative water content, specific leaf area and gas exchange during late development, and decreased head fresh weight, size, marketable and total yield. Deficit irrigation at 75% ETc had little influence on plant growth and physiology, but it still reduced both marketable and total yield. In 2013 season, 75% ETc irrigation had little influence on plant growth, leaf characteristics, photosynthetic rate, head fresh weight and size, but it temporarily increased chlorophyll and carotenoid content, and decreased stomata conductance, transpiration, and marketable yield. Pennant, the green-head cultivar, had higher photosynthetic rate, head fresh weight, marketable and total yield than the red-head cultivar Rio Grande. In both seasons, deficit irrigations did not influence cabbage head dry weight, indicating that most yield reduction under deficit irrigations is related to water content.  

The threecornered alfalfa hopper, Spissistillus festinus (Say), is a major pest to production of a wide variety of crops. Herbivory by this insect is often highly detrimental because of girdling of petioles and shoots. Although girdling by this hopper has been recorded on a variety of hosts, the physiological effects of girdling have been examined primarily on one host (Glycine max). We examined the physiological effects of girdling by four densities of hoppers on Arachis hypogaea (L.) cv. Florarunner. Densities of 0, 2, 4, and 6 hoppers per plant were maintained for a 1-week period on peanuts grown in cages in a greenhouse. Effects of hopper herbivory on growth (shoot elongation and increases in plant dry weight) and whole-plant chemistry (carbon, nitrogen, and amino acid analysis) were determined at the end of the 1-week feeding experiments, and again at 2-week intervals until maturation of plants. Differences in plant growth or chemistry were not apparent at the conclusion of the feeding experiment. However, plants subjected to the highest rates of herbivory showed pronounced deleterious effects 2 to 6 weeks after girdling had occurred. Mean shoot growth was decreased by nearly 40% and plant dry weight was reduced by roughly 20%. Foliar nitrogen concentrations were also significantly reduced; peanuts subjected to high rates of herbivory contained 30% less foliar protein that control plants. This delayed response to girdling appeared to be in part attributed to increased rates of shoot and petiole breakage well after girdling occurs. Girdles became more brittle as shoots matured and hardened with maturity. Effects of girdling may be particularly detrimental to yield, as effects are most pronounced as plants are entering the reproductive stage.

<p>Soil in the Fukushima area has been polluted with the radioactive contaminants such as Cs by the accident of Fukushima Daiichi nuclear power plant in March 2011. Remediation of soil contaminated with radioactive Cs remains one of the most important problems. Phytoremediation is an environmental remediation technique that takes advantage of plant physiology and metabolism to remove radioactive contaminants. Eleocharis acicularis is well known as heavy metal hyperaccumulator aquatic plant and expected as the strong candidate for application to Phytoremediation of polluted water and soil. In this study, a laboratory experiment was carried out to investigate the potential of E.acicularis for Phytoremediation of radioactive Cs contaminated site.The plants were grown hydroponically and placed in solutions containing Cs and K at different concentration (Cs concentration: 5 mg/L, K concentration: 0, 0.2, 2, 5, 50, 100 mg/L) in a period of 21days.In the experimental results, the highest concentration of Cs was 1560 mg/kg-DW in E. acicularis after 21 days. The concentration of Cs in plants decreased with the increasing initial concentration of K in the solution. This results indicate that E. acicularis has the ability to accumulate radioactive Cs from radioactive Cs contaminated soil and water, making it a good candidate species for radioactive Cs Phytoremediation.</p><p> </p><p><strong>Keywords</strong> : Fukushima, Eleocharis acicularis, phytoremediation, Cs</p>

A number of experiments with aquatic cultures of Far Eastern woody plants have been tested and proposed for use within the framework of specialized training in the classroom of elective courses in biology, laboratory work of ecological and biological centers. Regional material is aimed at developing students' interest in biology, deepening knowledge in the field of plant physiology and ecology.

Fertilization with essential mineral elements is important to get high quality yield results. The lack of necessary mineral elements in soil can affect oilseed rape plant physiological functions, photosynthesis and plant productivity. Oilseed rape plants have high requirements for nitrogen and as oil crop – for sulphur. The aim of the investigation was to explain changes of chlorophyll a fluorescence parameters in spring oilseed rape leaves and yield changes under nitrogen and sulphur supply. During laboratory experiments changes of chlorophyll a fluorescence parameters and during field experiments changes of yield parameters under different nitrogen and sulphur supply were observed. Laboratory and field experiments showed that sulphur fertilizer rate 18 kg ha-1 is the most effective sulphur dose for spring oilseed rape, when nitrogen 55 kg ha-1 is added, because its presence has positive effect on photosynthetic reactions. There was found out in laboratory experiments that chlorophyll a fluorescence parameters Fv/Fm and PI can be used to describe sulphur and nitrogen mineral element supply efficacy on spring oilseed rape. There was observed in the field experiment that oilseed rape yield increases significantly (from +0.34 t ha-1 to +0.64 t ha-1) under optimal (S18N55) nutrient supply, but lack of sulphur leads to significant yield losses. To avoid excessive fertilizer usage, its negative impact on plant physiology and yield losses, we consider that sulphur: nitrogen = 1:3 as additional fertilizer is optimal for spring oilseed rape plants.

Thesis (MTech (Agriculture)--Cape Peninsula University of Technology, 2018.<br>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.

En aquesta tesi presento quatre capítols, en els quals es discuteix com diferents espècies subarbustives interactuen amb plantes coexistents, sota règims variables d’estrès. Aquesta recerca ha estat centrada en ecosistemes de gran valor ambiental, ecològic i de conservació, i alhora sensibles als canvis ambientals, en quatre regions distintes situades en zones de latitud o altitud elevades. Per ordre latitudinal, els ecosistemes estudiats han estat: 1) el límit supraforestal dels Pirineus Centrals, situats en una zona temperada; 2) el gradient de successió primària d’un ecosistema situat en una zona boreal, a Finlàndia,; 3) el límit supraforestal situat a la zona subàrtica de Lapònia; i 4) la tundra situada en una zona de l’alt àrtic, al nord‐est de Grenlàndia . Els dos primers capítols es basen en una aproximació experimental i se centren en investigar com els subarbustos més comuns trobats prop del límit supraforestal interactuen amb plançons d’arbres de les espècies que formen el límit del bosc en dos ambients contrastats, i.e. el límit supraforestal subàrtic, i el límit supraforestal dels Pirineus Centrals. A més, donat que els arbres que viuen prop del límit de distribució són molt sensibles als canvis ambientals , especialment a l’augment de temperatures durant l’estació de creixement (Körner 2003), també s’ha investigat com podrien afectar el creixement dels plançons d’arbre i la seva supervivència al llarg de l’ecotò, diferents escenaris de canvis ambientals. El primer capítol es titula ‘Les interaccions arbre‐arbust i els canvis ambientals dirigeixen la dinàmica supraforestal a la zona subàrtica’, i s’hi exposa l’experiment de tres anys de durada que es va executar al ‘Parc Nacional d’Abisko’, en els Scandes subàrtics, al nord de Suècia; les plantes estudiades varen ser plançons de Betula pubescens i el subarbust Vaccinium myrtillus. En aquest estudi es va certificar la importància de les interaccions arbust‐arbre, tant facilitatives com competitives, com a elements clau en la dinàmica supraforestal subàrtica. A més, vàrem demostrar que la gran sensibilitat dels plançons a l’escalfament tenia fortes implicacions per la dinàmica supraforestal, tenint en compte l’escenari previst d’augment de temperatures en latituds elevades. També es va observar que les interaccions complexes entre arbusts i herbívors són claus per preveure canvis futurs. El segon capítol es titula ‘Els plançons d’arbres situats als límits supraforestals Pirinencs i subàrtics mostren respostes semblants a la presència d'arbustos i a les simulacions de canvis ambientals’. Aquí es presenta una comparació entre els resultats de l’experiment presentat en el primer capítol i els obtinguts en un experiment paral∙lel dut a terme durant un període de temps semblant prop del límit supraforestal en el ‘Parc Natural de l’Alt Pirineu’, als Pirineus Centrals catalans. Aquest experiment es va basar en el mateix disseny factorial que l’anterior estudi, però amb diferents espècies (i.e. plançons de l’arbre Pinus uncinata i l’arbust Rhododendron ferrugineum). Segons ens consta, és el primer estudi que avalua experimentalment les respostes de les plantes vers diferents escenaris ambientals en un ecosistema d’alta muntanya als Pirineus. En aquest capítol es presenten alguns mecanismes que ajudaran a comprendre la variabilitat recentment observada de les respostes locals de límits supraforestals de zones temperades i subàrtiques com a resultat del clima canviant, i també identifiquem alguns paral∙lelismes que poden utilitzar‐se per generalitzar les respostes a gran escala dels límits supraforestals al canvi climàtic. El tercer capítol se centra en els efectes d’un subarbust dominant (i.e. Empetrum nigrum) en plançons de Pinus sylvestris al llarg del gradient de successió primària en un ecosistema boreal en una illa emergent de la badia de Bòtnia, a Finlàndia. Aquest capítol s’anomena ‘Un arbust ericoide exerceix la doble funció de reclutar pins i els seus simbionts fúngics al llarg d’un gradient de successió primària’. Aquí hem mostrat que els efectes facilitadors i competidors dels subarbustos determinen fortament l’establiment de plançons i la seva colonització fúngica al llarg d’aquest gradient de successió. Segons ens consta, aquests són els primers resultats que demostren que un arbust ericoide micorrízic pot millorar tant el desenvolupament de l’arbre hoste ectomicorrízic com el dels simbionts fúngics de l’arbre. L’estudi presentat al quart capítol es va realitzar al llarg d’un gradient de nivositat en un ecosistema extrem de tundra àrtica al ‘Parc Nacional del nord‐est de Grenlàndia’, el Parc Nacional més gran del món. El capítol es titula ‘Interaccions vegetals i composició de la vegetació àrtica al llarg d’un gradient de nivositat al nord‐est de Grenlàndia’. Aquest ecosistema és probablement el més sensible i fràgil de tots els ecosistemes estudiats en aquesta tesi, donat que s’espera que a la costa est de Grenlàndia s’hi esdevinguin canvis substancials en el clima com a resultat de canvis destacables en els règims de precipitació de neu i de les temperatures (Brown i Mote 2009). Aquí es va avaluar la riquesa d’espècies de plantes, així com els patrons d’establiment i composició de diverses formes de creixement existents en comunitats vegetals àrtiques associades a una variació de la cobertura de neu durant els mesos d’hivern. Aquest estudi ajudarà a preveure la diversitat potencial i els canvis en la vegetació a la zona de l’alt Àrtic, si els règims de precipitació de neu canvien en el futur com es preveu.<br>In this thesis I present four chapters, and in all of them I discuss how dwarf shrubs interact with co‐occurring plants under varying regimes of stress. This research involved ecosystems of great environmental, nature conservation and ecological value, yet highly sensitive to environmental changes, in four contrasting cold regions at high altitude or high latitude. Following a latitudinal order, the selected ecosystems were: 1) a temperate alpine treeline in the Central Pyrenees; 2) a primary succession gradient in a boreal ecosystem in Finland; 3) a subarctic alpine treeline in Lapland; and 4) a high‐arctic tundra in north‐eastern Greenland. The first two chapters are based on an experimental approach and focus on how shrubs commonly found near the treeline interact with tree seedlings of treelineforming species in two contrasting environments, i.e. in a subarctic forest‐tundra ecotone in Lapland, northern Sweden, and in a more southern, temperate forestalpine pasture ecotone in the Central Pyrenees. In addition, since trees living near their limit of distribution are very sensitive to environmental changes, especially to increased temperature during the growing season (Körner 2003), we also assessed how distinct environmental change scenarios may affect tree seedling growth and survival across the ecotone. The first chapter is entitled ‘Shrub‐tree interactions and environmental changes drive treeline dynamics in the Subarctic’, where we explain the three‐year‐long experiment performed in the Abisko National Park, in the subarctic Scandes, Northern Sweden; the species studied were Betula pubescens tree seedlings and the shrub Vaccinium myrtillus. In this study we showed the importance of facilitative and competitive shrub‐tree interactions as drivers of subarctic treeline dynamics. Furthermore, we demonstrated that the great sensitivity of tree seedlings to warming had strong implications for treeline dynamics under the predicted warmer scenario at high latitudes, and we identified that complex interactions between shrubs and herbivores are critical to predicting future changes. The second chapter is entitled ‘Similar tree seedling responses to shrubs and to simulated environmental changes at Pyrenean and subarctic treelines’. Here we presented a comparison between the results obtained in the experiment presented in the first chapter and those obtained in a parallel experiment performed during a similar period near the treeline in the Alt Pirineu Natural Park, in the Central Pyrenees, Catalonia. This experiment was based on the same factorial design but with different species (i.e. Pinus uncinata tree seedlings and the shrub Rhododendron ferrugineum). To our knowledge, it is the first study which experimentally tests the responses of plants to distinct environmental scenarios in a high mountain ecosystem in the Pyrenees. In this chapter we presented some mechanisms for understanding the recently observed variability of local responses of both subarctic and alpine treelines to currently changing climate while identifying some commonalities that can be used to generalise large scale response of treelines to climate warming. The third chapter focuses on the effects of a dominant dwarf shrub (i.e. Empetrum nigrum) on Pinus sylvestris tree seedlings along a primary succession within a boreal ecosystem on an uplifting island in Bothnian Bay, Finland. This chapter is called ‘An ericoid shrub plays a dual role in recruiting both pines and their fungal symbionts along primary succession gradients’. Here we showed that facilitative and competitive effects of shrubs markedly determined tree seedling establishment and their fungal colonisation along this succession gradient, but in this chapter we did not relate these findings to any environmental changes. As far as we know, we presented the first finding that an ericoid mycorrhizal shrub may enhance both the performance of the ectomycorrhizal host tree and the tree’s fungal symbionts. The study presented in the fourth chapter was performed along a snow‐depth gradient in an extreme arctic tundra ecosystem in the Northeast Greenland National Park, the largest national park in the world. The chapter is entitled ‘Plant interactions and higharctic vegetation composition along a snow‐depth gradient in NE Greenland’. This ecosystem is probably the most sensitive and fragile among the ecosystems studied in this thesis as the eastern coast of Greenland is expected to experience substantial changes in climate due to marked changes in snow precipitation and temperature regimes (Brown and Mote 2009). Here we assessed plant species richness, establishment and composition patterns in distinct growth forms occurring in common arctic plant communities associated with varying snow‐depth during the winter season. This study will help to predict potential diversity and vegetation changes in the high Arctic if snow precipitation regime changes in the future as anticipated.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.<br>The experimental plant regulator XE-1019, a product of Chevron Chemical Company, was applied to short staple cotton at the University of Arizona Marana Agricultural Center in 1985. Plant height was modified by the chemical due to greatly shortened internode length. The 1.0 lb. a.i. XE-1019 per acre rate applied before bloom yielded significantly less than the other treatments at final harvest. Data collected from eight harvests through the season from sub-plots resulted in significant yield differences from the second through the sixth harvest dates.

<p>Copper and Zn deficiencies of crop plants occur in various areas throughout the world. The sulfate forms of Cu and Zn are generally used to correct these micronutrient deficiencies. In agricultural practices, Cu and Zn are applied to soils not only as a fertilizer but also as manures, pesticides and waste materials such as sewage sludge. High levels of Cu and Zn application to agricultural soils are considered to pose a potential hazard to plants and animals. Research findings have not established Cu and Zn levels that either injure plants or increase Cu and Zn concentrations in edible plant portions to undesirably high levels. Published data on the fate of applied Cu and Zn indicate that there is little, if any, downward movement of these micronutrients in soils and that, with time, applied Cu and Zn revert to plant unavailable forms in soils. </p><br>Master of Science

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.<br>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.

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.<br>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.

Els cloroplasts presenten una activitat respiratòria anomenada clororespiració, que consisteix en una cadena de transport electrònic des del NAD(P)H fins a l’oxigen i que està situada a les membranes tilacoidals. En aquesta cadena respiratòria participen el complex NAD(P)H deshidrogenasa (Ndh), la plastoquinona i la oxidasa terminal plastidial (PTOX). La seva funció està probablement relacionada amb l’adaptació de la fotosíntesi en situacions d’estrès o davant dels canvis en l’ambient. La possible existència d’una activitat respiratòria en plastidis no fotosintètics ha estat molt poc estudiada. Durant la maduració del tomàquet, els cloroplasts del fruit verd es diferencien en cromoplasts, els quals acumulen carotenoides i són fotosintèticament inactius. Durant aquest procés les membranes tilacoidals es desmantellen i l’aparell fotosintètic es degrada. No obstant, diversos transportadors electrònics es mantenen (Ndh, citocrom b6f i PTOX), així com l’ATP sintasa. Aquest fet suggereix que els cromoplasts podrien mantenir una activitat respiratòria similar a la clororespiració. En aquest treball es van realitzar estudis de respiració utilitzant cromoplasts aïllats de tomàquets madurs. Es va observar que els cromoplasts consumeixen oxigen activament, i aquest consum és estimulat pels donadors d’electrons NADH i NADPH. A més, la respiració de cromoplasts respon al desacoblador CCCP, suggerint que possiblement està relacionada amb la creació de gradients de protons a través de membranes. Per últim, es va comprovar que el consum d’oxigen és inhibit per un inhibidor de la PTOX, l’octil gal·lat, indicant que la PTOX és l’oxidasa terminal de la cadena respiratòria. Per altra banda, es va observar que els cromoplasts aïllats són capaços de sintetitzar ATP en presència de NADH i NADPH. Igual que el consum d’oxigen, la síntesi d’ATP és inhibida per l’octil gal·lat i respon al CCCP. Es van realitzar mesures en presència d’un inhibidor específic del complex citocrom b6f i la síntesi d’ATP va quedar parcialment inhibida, la qual cosa suggereix que el citocrom b6f participa en la cromorespiració. A més, es va estudiar l’efecte d’un inhibidor de les NAD(P)H deshidrogenases i es va observar que produïa un efecte diferent segons el donador d’electrons emprat, suggerint la presència de dues NAD(P)H deshidrogenases diferents. Per confirmar la presència del citocrom b6f en els cromoplasts, es va fer un estudi per tècniques d’immunocitoquímica fent servir un anticòs contra el citocrom f i es va localitzar a l’interior dels cromoplasts de tomàquet. En la cromorespiració, un possible acceptor d’electrons per al citocrom b6f és el citocrom c6, doncs es va observar que la seva expressió augmenta durant la maduració. Per altra banda es va intentar identificar una possible NAD(P)H deshidrogenasa alternativa al complex Ndh que participés en la cromorespiració. Les NAD(P)H deshidrogenases tipus II (Ndh-2) són enzims monomèrics que es troben a plastidis, mitocondris i peroxisomes. El genoma del tomàquet conté set gens que codifiquen Ndh-2. Es va estudiar l’expressió dels set gens en diversos teixits de tomaquera i durant la maduració del tomàquet, i es va trobar que quatre Ndh-2 són presents en el fruit madur. A continuació, es va estudiar la seva localització subcel·lular mitjançant la fusió d’aquestes Ndh-2 amb la YFP i l’expressió transitòria de les proteïnes quimèriques en fulles de plantes de tabac, i es va comprovar que dues Ndh-2 són plastidials. Per tant, aquestes Ndh-2 són candidates que podrien participar en la cromorespiració. Per comprovar quina podia ser la contribució de la cromorespiració en relació a la respiració total del tomàquet, es van realitzar estudis amb fragments de pericarp fent servir l’inhibidor octil gal·lat. Els resultats obtinguts mostren que la respiració associada a l’activitat de la PTOX augmenta durant la maduració del fruit i representa un 25% de la respiració total quan és madur. A més, també es va comprovar que la cromorespiració contribueix significativament al contingut d’ATP total del pericarp de fruit madur.<br>Chloroplasts present a respiratory process called chlororespiration. This activity consists in an electron transport pathway from NAD(P)H to oxygen which it is located in thylakoidal membranes, and it involves the plastidial terminal oxidase (PTOX) and the NAD(P)H dehydrogenase complex (Ndh). Its function is related with photoprotection and the adaptation of photosynthesis in changing environmental conditions. However, the existence of a similar respiratory process in non-photosynthetic plastids was less studied. During tomato (Solanum lycopersicum) fruit ripening, chloroplasts differentiate into photosynthetically inactive chromoplasts. In this work, we have shown that isolated tomato fruit chromoplasts present an oxygen consumption activity which is stimulated by the electron donors NADH and NADPH. This respiratory activity is sensitive to the uncoupler CCCP, suggesting that it could be related to the generation of membrane proton gradients. It is also affected by octyl gallate (Ogal), a PTOX inhibitor. The ATP synthesis rate of isolated chromoplasts was quantified, and we observed that it is dependent on the supply of NAD(P)H and is fully inhibited by Ogal. Also, the ATP synthesis is sensitive to a cytochrome b6f complex inhibitor, and the possible participation of this complex in chromorespiration is supported by the detection of cytochrome f in chromoplasts using immunoblot and immunocytochemical techniques. The observed increased expression of cytochrome c6 during ripening suggests that it could act as electron acceptor of the cytochrome b6f complex in chromorespiration. In addition, we studied the family of type II NAD(P)H dehydrogenases in tomato (Ndh-2), which includes seven genes. Four Ndh-2 are expressed in ripe tomato fruit, and two of them (nda2 and ndc1) are located in plastids, so they are candidates to participate in chromorespiration. On the other hand, the effects of Ogal on respiration and ATP levels were also studied in tissue samples. Oxygen uptake of mature green fruit and leaf tissues was not affected by Ogal, but was inhibited increasingly in fruit pericarp throughout ripening (up to 25% in red fruit). Similarly, Ogal caused a significant decrease in ATP content of red fruit pericarp. The number of energized mitochondria, as determined by confocal microscopy, strongly decreased in fruit tissue during ripening. Therefore, the contribution of chromoplasts to total fruit respiration appears to increase in late ripening stages.

The biological actions of the herbicides SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate) and glyphosate [N-(phosphonomethyl)glycine] (PMG) were compared. In each study trimethylsulfonium iodide (TMS-I) was included as a treatment because the trimethylsulfonium ion is a constituent of the SC-0224 molecular structure. In inflated duckweed (Lemna gibba L.), both formulated and technical grade forms of SC-0224 were found to be much more phytotoxic to duckweed than either formulated or technical grade forms of glyphosate. The growth inhibition caused by glyphosate was partially prevented by different combinations of the aromatic amino acids phenylalanine, tyrosine, and tryptophan; whereas, the duckweed growth inhibition caused by SC-0224 could not be reduced by the same amino acid combinations. TMS-I and SC-0224 were found to be equally phytotoxic to duckweed. SC-0224 caused larger increases than glyphosate in the pool levels of amino acids; the increases caused by SC-0224 were similar, however, to those caused by trimethylsulfonium iodide. Expressed on a per gram fresh weight basis none of the chemical treatments caused significant changes in soluble protein or the incorporation of ¹⁴C-leucine into soluble protein. On a per flask basis (allowing for decreased growth in treated flasks), both herbicides and TMS-I caused significant decreases in soluble protein and ¹⁴C-leucine incorporation. SC-0224 and TMS-I caused larger decreases than glyphosate in both cases but the SC-0224 and TMS-I treatments were not significantly different. These data indicate that differences in the phytotoxicity of SC-0224 .and glyphosate may be due to the action of the trimethylsulfonium ion of the SC-0224 structure. The effects of these herbicides on the conversion of shikimate to anthranilate in a cell-free extract of Klebsiella pneumoniae ATCC 25306 were also compared. SC-0224 and glyphosate equally inhibited the production of anthranilate indicating that SC-0224 has action similar to glyphosate on the shikimate pathway. The effects of these herbicides on photosynthetic electron transport (the Hill reaction) was determined using isolated thylakoids from Alaska pea (Pisum sativum L.). The action of SC-0224 was compared with the action of glyphosate, TMS-I and diuron [3-(3,4-dichorophenyl)-1,1-dimethylurea]. SC-0224, glyphosate and TMS-I did not inhibit the Hill reaction at concentrations up to 10 mM; whereas, diuron caused an almost total inhibition at 0.10 mM. The results of this study indicate that SC-0224 is not an inhibitor of photosynthetic electron transport. These studies indicate that both constituents of the SC-0224 structure, TMS and PMG, are phytotoxic and may act independently.<br>Ph. D.

Environmental constraints and developmental processes in plants can lead to light energy excess in chloroplasts by lowering the threshold at which light becomes saturating by a lack of electron acceptors in the light-processing structures. Inactivation of photosystems due to high energy quanta is generally known as photoinhibition, a process that can compromise growth and organ development in plants due to an imbalance of the cellular redox state that leads to enhanced oxidative stress. Hence, it is essential to determine environmental factors and stages of organ development that influence the extent of photoinhibition and mechanisms triggered to avoid photoinhibition and cope with photo-oxidative stress, so that plant survival is not put in jeopardy. For this reason, leaves from an ecologically important Mediterranean plant, flowers from a relevant commercial crop and fruits from a highly appreciated agronomic tree, were selected to analyse events leading to photoinhibition and strategies to allow plant acclimation and correct organ development. With this regard, mastic trees were selected to study their sensitivity to cold stress during Mediterranean winters and altitudinal distribution, to determine if antioxidant strategies and leaf phenology influence their ability to survive environmental constraints. On the other hand, lily flowers were selected to study photoinhibitory events taking place during flower opening and how phytohormones could regulate the timing of flower opening by interacting with photo-oxidative stress signals. Besides, sweet cherry fruits were also selected to better understand physiological events related to ripening onset and chloroplast dismantling with the production of antioxidants and hormonal signals involved. Our results show that timing and stage of organ development directly condition the outcomes of photoinhibition with regards of chloroplast status and antioxidants produced, with a general prevailing mechanism where reduced Fv/Fm triggers higher lipid peroxidation and parallel production of phytohormones and antioxidants that deal with increased photo-oxidative stress. In conclusion, photoinhibition does not compromise plant or organ survival, but prompt the activation of signalling networks that promote metabolic changes to fine-tune the timing and severity of this process to allow acclimation and correct organ development.

This paper covers the new field of thermally adaptive building coverings, their inspiration, basic operational characteristics, analytical modeling and coupon testing. Inspiration for thermally adaptive building coverings come quite notably from various families of thermotropic plant structures. Certain plant cellular structures like those in Mimosa Pudica (Sensitive Plant), Rhododendron leaves or Albizia Julibrissin (Mimosa Tree), exhibit actuation physiology which depends on physical manipulation and/or thermal loading as a function of solar radiation. The paper draws parallels between the differential actuation via cellular turgor pressure manipulation. A parallel with these structures can be seen in the new field of thermally adaptive building coverings which use various forms of cellular foam to aid or enable actuation much in the same way that plant cells are used to move leaves. When exposed to high solar loading, the structures curve upwards and outwards. When cold, these same structures curve back towards the building forming convex pockets of dead air to insulate the building. The paper shows the basic classical laminated plate theory models comparing theory and experiment of such coupons. The study concludes with a basic description of the effectiveness of thermally adaptive building coverings.

Maritime and air traffic through the Arctic has increased in recent years. Cruise ship and commercial jet liners carry a large number of passengers. With increased traffic, there is a higher probability that a major disaster could occur. Cruise ship and plane accidents could be catastrophic and may require mass rescue. Due to the remote location, limited search and rescue resources, time for these resources to get to the accident location and large number of survivors, the retrieval time could be several days. Therefore, survivors may be required to survive on their own for days while they await rescue. Recognizing that the International Maritime Organization does not have specific thermal performance criteria for liferafts and lifeboats and personal and group survival kits, the Maritime and Arctic Survival Scientific and Engineering Research Team (MASSERT) initiated a research project to improve safety and provide input for advances to regulations. The objective of the project is to investigate if the current thermal protective equipment and preparedness available to people traveling in the Canadian Arctic are adequate for surviving a major air or cruise ship disaster and to identify the minimum thermal protection criteria for survival. This project builds on the results and tools developed in other research projects conducted by the team on thermal protection of liferafts, lifeboats and immersion suits. The project is divided into three major phases — clothing ensemble testing with thermal manikins, a physiology experiment on sustainable shivering duration and ensemble testing in Arctic conditions with human subjects. A numerical model uses these data to simulate survival scenarios. In the first phase of this project, the thermal resistance values of the protective clothing typically available to cruise ship and aircraft passengers were measured using two thermal manikins. The ensembles included Cabin Wear, Deck Wear, Expedition Wear, Abandonment Wear and protective clothing from Canada Forces Major Air Disaster Kit (MAJAID). Tests were conducted on dry and wet ensembles at 5°C and −15°C with and without wind. There is very good agreement between the thermal resistances measured by the two manikins. The differences in thermal resistances observed are likely caused by variations in fit and wrinkles and folds in the ensembles from dressing. With no wind, the thermal resistance is lowest with Cabin Wear and highest with MAJAID clothing inside the down-filled casualty bag. The Expedition Wear, the Abandonment Wear and the MAJAID clothing have about the same thermal resistance. With 7 metre-per-second wind, the thermal resistance of all ensembles decreased significantly by 30% to 70%. These results highlight the importance of having a shelter as a windbreak. For wet clothing ensembles at 5°C, the initial wet thermal resistance was 2 to 2.5 times lower than the dry value, and drying times ranged up to 60 hours. This highlights the importance of staying dry. Preliminary predictions from the numerical model show that the survivors in Expedition Wear, even with sleeping bag and tent, can be mildly hypothermic and need to depend heavily on shivering to maintain thermal balance. In a shelter, the predicted metabolic rate is roughly double the resting rate; it is triple the resting rate without protection from the wind. Further research is required to study shivering fatigue and age effects. Research on mass rescue scenarios for cruise ships and airplanes survivors should ideally involve subjects of both genders and the elderly.