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1
James, Andrew Thomas. "Genotypic variation in soybean for drought stress response /." St. Lucia, Qld, 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17408.pdf.
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Batlang, Utlwang. "Identification of Drought-Responsive Genes and Validation for Drought Resistance in Rice." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/26020.
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Drought stress was studied in rice (Oryza sativa) and maize (Zea mays) to identify drought-responsive genes and associated biological processes. One experiment with rice examined drought responses in vegetative and reproductive tissues and identified drought-responsive genes in each tissue type. The results showed that brief periods of acute drought stress at or near anthesis reduced photosynthetic efficiency and ultimately lowered grain yield. Yield was reduced as a result both of fewer spikelets developed and of lower spikelet fertility. Affymetrix arrays were used to analyze global gene expression in the transcriptomes of rice vegetative and reproductive tissue. Comparative analysis of the expressed genes indicated that the vegetative and reproductive tissues responded differently to drought stress.
An experiment was conducted with maize, using GS-FLX pyrosequencing to identify differentially expressed genes in vegetative and reproductive tissues; and these results were compared with those from the just-described rice transcriptome. Some of the drought-responsive genes in the maize reproductive tissue were validated by quantitative real time polymerase chain reaction (qRT-PCR). The differentially expressed genes common to both maize and rice were further analyzed by gene ontology analysis to reveal core biological processes involved in drought responses. In both species, drought caused a transition from protein synthesis to degradation, and photosynthesis was one of the most severely affected metabolic pathways.
In a validating experiment, a drought-responsive transcription factor found in rice and dubbed HIGHER YIELD RICE (HYR) was constitutively expressed in rice, and the transgenic HYR plants were studied. Under well-watered conditions, the HYR plants developed higher rates
of photosynthesis, greater levels of soluble sugars (glucose, fructose, and sucrose), more biomass, and higher yield. They also exhibited a drought-resistant phenotype, with higher water use efficiency, photosynthesis, and relative leaf water content under drought stress. Taken together, these studies demonstrate the potential value of newer technologies for identifying genes that might impart drought resistance and for using such genes to make crops more productive either in the presence or in the absence of drought stressPh. D.
3
Tahkokorpi, M. (Marjaana). "Anthocyanins under drought and drought-related stresses in bilberry (Vaccinium myrtillus L.)." Doctoral thesis, University of Oulu, 2010. http://urn.fi/urn:isbn:9789514262050.
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Abstract
The aim was to study the effects of drought and indirect drought-related stresses on anthocyanin content in bilberry (Vaccinium myrtillus L.). Anthocyanin content was also studied in relation to developmental stage (juvenile vs. mature leaves, previous vs. current-year stems). It was hypothesised that drought-stressed plants accumulate anthocyanins, but their direct role in osmotic regulation was questioned.
Direct drought was created by preventing water supply. Freezing-induced dehydration was accomplished by removal of snow. Effects of summertime chilling (+2 °C during active growth, +5/0 °C during frost hardening) on water status were tested. The trace metal Nickel (Ni) was applied to the soil, as Ni may interfere with plant water relations at the rhizospheric level. Salt (Na+) was added to the soil to observe salt-induced disturbance in osmotic balance and ion homeostasis.
Tissue water content (TWC) decreased and anthocyanin level increased under direct drought, especially in the mature leaves. The freezing-stressed plants contained the same TWC and anthocyanin levels in mid-winter compared to plants that overwintered below snow. The freezing-stressed plants had lower TWC and a similar anthocyanin level in early spring, and lower TWC and anthocyanin level in late spring than plants that overwintered below snow. In the summer and autumn following snow removal, current-year stems of freezing-stressed plants had the same TWC, but higher levels of anthocyanins than current-year stems of plants that overwintered below snow. New growth was thus affected by the freezing stress experienced by previous-year stems. Chilling had no effect on anthocyanins. Although TWC decreased and anthocyanin level increased from active growth to the beginning of frost hardening, no increase was observed during frost hardening. Ni did not cause drought stress in the aboveground shoots, but anthocyanin level decreased in the aboveground shoots along with Ni accumulation in the belowground stems. Na+ increased TWC in the belowground stems, but decreased TWC and anthocyanin level in the aboveground stems.
It is proposed that anthocyanins do not have direct role in osmotic regulation, or in the development of freezing tolerance. It is suggested that the increase in anthocyanin level under direct drought stress is mainly due to the photoprotection of chlorophylls by anthocyanins. This is supported by two facts: (1) At increased anthocyanin level in the juvenile leaves, chlorophyll a was stabilized despite continuing drought stress, and (2) after the initial peak in the mature leaves, the accumulation of anthocyanins ceased although the drought became more severe. As chlorophyll a decreased in the mature leaves due to senescence, there was less demand for such high levels of anthocyanins.
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Gebeyehu, Setegn. "Physiological response to drought stress of common bean (Phaseolus vulgaris L.) genotypes differing in drought resistance." Göttingen Cuvillier, 2006. http://geb.uni-giessen.de/geb/volltexte/2006/3726/index.html.
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Glass, Vimy M. "Drought stress effects in wild blueberries (Vaccinium angustifolium Ait.)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0017/MQ57237.pdf.
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Leblanc, Rosanne. "Protein synthesis and drought stress in two rapeseed cultivars." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60487.
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Desiccation effects on rate and pattern of protein synthesis in Brassica napus (cv westar) and Brassica juncea (cv cutlass) have been examined. Results showed that while the rate of water loss was similar in the two species, the inhibition of amino acid incorporation was greater in B. napus than B. juncea at any given level of desiccation. Electrolyte leakage increased with the degree of desiccation and was greater in B. napus than in B. juncea. In both, the increase in leakage was much sharper after 12 hours of desiccation. Quantitative changes in patterns of boiling-stable protein synthesis due to desiccation stress were observed. The control level of protein radioactivity which was boiling-stable in B. napus was 16.16% and 19.96% for B. juncea. After desiccation, the percentage of boiling-stable radioactivity increased to 23.30% for B. juncea and 16.63% for B. napus. In vitro translation of total RNA indicated that desiccation alone does not induce the synthesis of new mRNA species in either cultivar, but it may change the translation pattern resulting in different levels of abundance of proteins.
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urbanovski, Nada. "PIP aquaporins and drought stress responses in Fragaria spp." Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534841.
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Li, Xiaoqing. "Plant root development and hormone signalling during drought stress." Thesis, Lancaster University, 2016. http://eprints.lancs.ac.uk/79357/.
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The plant root system is crucial for plant survival, growth and development, and it plays an important role in plant resistance to drought stress. Drought is one of the primary factors that restrict plant growth and yield, and its threat to crop yields will increase along with the growing food demand by the population of a world experiencing a changing climate. In response to drought in plants, various hormones are vital regulators, because they are able to manipulate plant development and in some cases minimise the adverse impact of drought. Therefore, understanding how the plant root system will adapt to a soil drying challenge is crucial. Of particular importance is the plant response to a non-lethal drought stress, which is often encountered in the field. Elucidation of the mechanisms underlying such responses, including hormonal regulations, may help crop scientists improve the plant performance under drought. A six-day progressive soil drying pot experiment was designed to examine the synchronisation of physiological responses in maize (Zea mays L.) roots and leaves during soil drying. It was found that maize roots showed earlier responses to soil drying than leaves in changing growth rates, water potentials and hormone levels. Root growth was stimulated at soil water content of 25−32% (ca. 41% in well-watered pots), while both root growth and leaf elongation were inhibited when soil water content was below 20%. Root abscisic acid (ABA) level gradually increased when soil water content was lower than 32% during soil drying. The stimulation and inhibition of root growth during soil drying may be regulated by root ABA, depending on the degree of the concentration increase. The ethylene release rates from leaves and roots were inhibited during soil drying, which occurred later than the increase in ABA levels. In a subsequent root phenotyping study on 14 maize genotypes, significant genetic variation was observed in root angle and size (root length, surface area and dry weight), and in the plasticity of these traits under mild and severe drought stress. Genotypes with a steeper root angle under well-watered conditions tended to display more promotion or less inhibition in root size under drought. Further analysis showed that combined traits of maize root angle, its plasticity and the root size plasticity under drought may be a better predictor for maize drought resistance than a single one of these traits. Moreover, root angle was found positively related to the leaf and root ABA levels and negatively related to the root tZ (a cytokinin) level under well-watered conditions. In another study on the crosstalk of drought-related hormones using the model plant Arabidopsis thaliana L., the biphasic responses of root elongation to ABA were confirmed, i.e. low external ABA concentrations stimulated root growth while high ABA concentrations inhibited it. Furthermore, ethylene and auxin were found to be involved in these responses. The inhibitory effect of high ABA levels on root growth was reduced or even eliminated when Arabidopsis was chemically treated to inhibit the ethylene biosynthesis or signalling, or to block auxin influx carriers. This was confirmed using mutants with blocked ethylene or auxin signalling, or a defect in the auxin influx carrier AUX1. On the other hand, the stimulatory effect of low ABA levels on root growth was lost when Arabidopsis seedlings were chemically treated to inhibit the auxin efflux carriers, and in mutants with blocked auxin signalling or with a defect in the PIN2/EIR1 auxin efflux carrier. These results indicate that ABA regulates root growth through two distinct pathways. The inhibitory effect that operates at high ABA concentrations is via an ethylene-dependent pathway and requires auxin signalling and auxin influx through AUX1. The stimulatory effect that operates at low ABA concentrations is via an ethylene-independent pathway and also requires auxin signalling and auxin efflux through PIN2/EIR1. This research contributes to our understanding of the responses of plant root system to different degrees of non-lethal drought stress, and it highlights the importance of root traits that may be important to plant drought resistance. The potential involvement of hormones (ABA, ethylene, auxin and cytokinin) in these processes is clarified. The knowledge gained may be integrated in novel crop management strategies to plan irrigation and help in the development of drought resistant crop varieties.
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Atkinson, Nicola Jane. "Plant molecular response to combined drought and nematode stress." Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/2131/.
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Plants are adapted to respond to precise environmental stress conditions, activating specific molecular and physiological changes in order to minimise damage. Response to multiple stresses is therefore different to that to individual stresses. Simultaneous biotic and abiotic stress conditions are of particular interest, as the molecular signalling pathways controlling each interact and antagonise one another. Understanding such processes is crucial for developing broad-spectrum stress-tolerant crops. This study characterised the molecular response of plants to the concurrent stresses of drought (abiotic stress) and infection with plant-parasitic nematodes (biotic stress). Drought stress increased susceptibility to infection with Heterodera schachtii in Arabidopsis thaliana. The whole-genome transcriptome response to these stresses was analysed using microarrays. Each stress induced a particular subset of differentially expressed genes. A novel programme of gene expression was activated specifically in response to a combination of drought and nematode stress, involving 2394 differentially regulated genes. A diverse range of processes was found to be important in the response to multiple stresses, including plant hormone signalling, activation of transcription factors, cell wall modification, production of secondary metabolites, amino acid metabolism and pathogen defence signalling. Ten multiple stress-induced candidate genes were selected and their functions investigated using over-expression lines and loss-of-function mutants. Altered susceptibility to drought stress (TCP9, AZI1, RALFL8) and nematode infection (TCP9, RALFL8, ATMGL, AZI1) was observed in several of these lines. The effect of combined drought and nematode infection on nutritional parameters of tomato fruits was analysed. Drought stress lengthened flowering time and negatively affected carotenoid accumulation. Infection with Meloidogyne incognita reduced yield and ripening time and had a positive effect on the accumulation of phenolic compounds. The stresses in combination increased fruit sugar content. This work comprises the first whole-genome transcriptome study into combined abiotic and biotic stress. The results highlight the importance of studying stress factors in combination.
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Raney, Joshua Arthur. "Transcriptome Analysis of Drought Induced Stress in Chenopodium Quinoa." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3915.
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RNA-seq transcriptome analysis of Chenopodium quinoa at different water treatment levels was conducted in a greenhouse study using four water treatments (field capacity to drought) on a valley ecotype quinoa (variety Ingapirca) and an Altiplano Salares ecotype quinoa (variety Ollague). Physiological results support the earlier findings that the Salares ecotypes display greater tolerance to drought-like stress conditions than the valley ecotypes (as determined by growth rate, photosynthetic rate, stomatal conductance, and stem water potential). cDNA libraries from root tissue sample for each treatment x variety combination were sequenced using Illumina Hi-Seq technology in an RNA-seq experiment. De novo assembly of the transcriptome generated 20,337 unique transcripts. Gene expression analysis of the RNA-seq data identified 462 putative gene products that showed differential expression based on treatment and 27 putative gene products differential expressed based on variety x treatment, including significant increasing expression in the root tissue in response to increasing water stress. BLAST searches and gene ontology analysis show an overlap with drought tolerance stress and other abiotic stress mechanisms.
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Dewey, Daniel Wade. "Physiological and genetic control of water stress tolerance in zoysiagrass." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3172.
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Significant cultivar difference in many water stress responses of zoysiagrass
(Zoysia japonica (Steud.) and Zoysia matrella (L.) Merr.) are shown in this study. Of the
four cultivars, Palisades was the most water stress tolerant, had the most negative turgor
loss point, and leaf rolled after loss of full turgor pressure. On the other end of the
spectrum, Diamond was the least water stress tolerant, had the lowest full turgor pressure,
the least negative turgor loss point, and leaf rolled at full turgor. Differences between
Diamond, Cavalier, Palisades, and DALZ 8504 in leaf rolling, loss of full turgor, water
release curve parameters, root characteristics and gene expression make zoysiagrass a
prime candidate for further investigation into the mechanisms of water stress
avoidance/tolerance. Enhanced antioxidant activity and stomatal control, along with root
characteristics, most likely explain the cultivar difference in water stress tolerance of
zoysiagrass. Palisades and DALZ 8504 maintained full turgor for significantly longer
than Diamond and Cavalier, which may be associated with root characteristics and/or
enhanced stomatal control as only those two cultivars showed enhanced expression of a
stomatal control gene (phospholipase D). The apparent response (most apparent in turgid
weight/dry weight ratios (TWDW)) of well watered plants to water stressed neighbor plants will likely be the most novel finding of this study. Well watered zoysiagrass and
Kentucky bluegrass responded to water stressed neighbors by reducing TWDW.
Significant increases in gene expression of a systemin degrading enzyme and of an
integral membrane protein (signal receptor) were also observed in well watered plants.
Results from this study indicate that this phenomenon is occurring and expose a dearth in
scientific understanding that must be filled. Improving water stress tolerance through
breeding for parameters like those discussed in this paper (delayed leaf rolling or loss of
full turgor, enhanced stomatal control, enhanced antioxidant activity, deep rooting
characteristics, etc.) may very likely produce turfgrasses that can survive and maintain
desired aesthetic qualities using significantly less water.
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Simpson, Katrina Lynn Scott. "Interactions between aphids and their host plants under drought stress." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8294.
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Interactions between host plants and aphids under water stress conditions were examined. Two controlled environment room studies, a Veld experiment and phenological modelling analysis were used to investigate three different plant-aphid relationships. The aim of these studies was to determine the results of water shortage on plant and pest populations, which are likely to result under climate change scenarios. The central hypothesis was that mild drought stress would lead to greater aphid populations through a beneficial increase of small nitrogenous molecules in the phloem sap providing improved diet quality — the Plant Stress Hypothesis (White, 1969). Myzus persicae (the peach–potato aphid) is a broad-range feeder with a preference for senescent foliage. Contrary to expectations, on young cabbage plants, Brassica oleracea var capitata, it was found to increase faster and to a greater extent on well-watered hosts. Aphids were also found to prevent osmoregulation in droughted plants. Despite this, the aphid infestation led to a drought-like response in all plants irrespective of watering regime, causing significantly reduced growth. Metopolophium dirhodum (the rose–grain aphid) overwinters as eggs on Rosa spp. but most of its life-cycle is spent on grasses and cereal crops. As with M. persicae, aphid infestation caused drought-like symptoms even in well-watered plants. The mechanism of reduction in plant health is most likely through aphid damage to the efficiency of Photosystem a within 7 days of infestation. On young barley plants, Hordeum vulgare, the rose–grain aphid was found to increase faster and to greater extent on droughted hosts. In contrast to M. persicae, the study strongly supported the Plant Stress Hypothesis, Finding that even mild water stress of approximately −0.3 MPa could lead to conditions favourable to rapid aphid population increase. The difference in the response of different species of aphids may be associated more with the levels of soluble nitrogen in their diet than specifically host plant water status. Drepanosiphum platanoidis is an aphid specific to sycamore, Acer pseudoplatanus and spends its entire life-cycle on that species. In the Veld, the total number of aphids supported by a single tree was found to correlate most strongly with soluble leaf nitrogen. In addition, the number of aphids on individual leaves was found to correlate strongly and negatively with stomatal conductance and leaf water potential. Finally, analysis of historical aphid suction-trap data was carried out. UK Rothamsted suction-traps are 12.2 m tall and sample air at 0.75 m3 s-1, with daily aphid sampling between April and November. The traps are designed to catch the largest proportion of aphids in the total insect sample and to reduce the effect of surrounding land-use on the sample. The area represented by a trap may be as much as 700 km2 (Harrington and Woiwod, 2007). The dataset is the longest and most geographically extensive for aphid populations, comprising 46 sites across Europe as of 2011. In this analysis, aphid and meteorological data from the Edinburgh East Craigs site were used. This also enabled comparison with D. platanoidis numbers collected in the Veld, which showed a strongly significant positive relationship between the two. Since the data collected in suction-traps are correlated with numbers in the Veld, aphid population analysis can be improved with use of these longer datasets, without reliance on shorter-term Veld surveys. The various population characteristics examined were found to be strongly correlated with each other, but were unconnected to data from previous years. The date of first catch was found to be significantly advancing over time, with strong influences from daily minimum temperatures and vapour pressure deficits of the air within the year. Higher temperatures with lower humidity tend to bring forward the date of first catch. Lower tends to depress the population in the summer. The overall hypothesis that mild drought would benefit aphid populations cannot be accepted, but in two cases of the experiment sections of the work there were strong relationships between aphid numbers and both leaf temperature and soil moisture. The meteorological data analysis indicates that climatic changes towards a hotter, drier climate could substantially alter population dynamics. Harrington, R. and Woiwod, I. (2007). Foresight from hindsight: The Rothamsted Insect Survey. Outlooks on Pest Management, 18, 9–14. White, T. (1969). An index to measure weather-induced stress of trees associated with outbreaks of psyllids in Australia. Ecology, 50, 905–909.
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Banfield-Zanin, Jennifer A. "The effect of drought stress on the green spruce aphid." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/18966.
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The green spruce aphid, Elatobium abietinum (Walker) (Hemiptera: Aphididae), is the most important defoliating pest of Sitka spruce, Picea sitchensis (Bong.) Carr., in the U.K. Currently, populations of this aphid are limited by freezing periods in the winter, while interactions between climate and other factors regulate population dynamics. Climate change in the U.K. is predicted to result in: (1) warmer winters, improving overwinter survival by aphid populations, and (2) an increase in hot and dry summers, likely to place Sitka spruce under drought stress. These could promote aphid densities and increased damage to the trees, resulting in losses to plant growth and productivity. Few studies have been conducted on the effect of drought stress on arboreal herbivores. This project sought to explore the effects of different intensities of spring-summer drought stress on E. abietinum on Sitka spruce. Populations and their effects on their host plant, in terms of needle retention and impact on tree growth, were observed in a semi-field nursery setting. The performance of individual aphids was also observed under controlled conditions at intervals following bud-burst in spring, and again in autumn. Finally, a study was conducted on the consumption rates of specialist and generalist Coccinellid predators feeding on aphids reared under differing drought intensities. Elatobium abietinum exhibited an overall positive response to moderate intermittent drought stress, while severe stress was typically detrimental. When considered with aphid size, Coccinellid predator consumption rates reflected these findings. Changes to damage levels on Sitka spruce can therefore be expected under drought stress; increases are likely under moderate intermittent stress, though the nature of changes under severe stress levels remain unclear. The results revealed complex interactions between drought stress, E. abietinum and Sitka spruce. Given the potential impact of the aphid, it is important to understand the possible responses under climate change.
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Wendelboe-Nelson, Charlotte. "A proteomic analysis of drought stress in barley (Hordeum vulgare)." Thesis, Heriot-Watt University, 2012. http://hdl.handle.net/10399/2573.
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Drought is a major threat to world agriculture. In order to identify proteins associated with plant drought tolerance, barley varieties bred in the UK (Golden Promise) and Iraq (Basrah) were compared. The variety Basrah showed physiological adaptations to drought when compared to Golden Promise, for example relative water content after one week of drought was much higher for Basrah than for Golden Promise in the leaves as well as the roots. Also the water loss rate was significantly different between the two varieties, with the Basrah variety loosing water at about half the rate of Golden Promise. DIGE analyses were carried out on proteins from roots and leaves under control and drought conditions. 24 leaf and 45 root proteins were identified by MALDI-TOF MS spectrometry. The relative expression patterns of the identified proteins fell into a number of distinct classes. The variety Basrah is characterised by constitutive expression or higher drought-induced expression levels of proteins regulating ROS production and protein folding. Photosynthetic enzymes, by contrast, were downregulated in Basrah. Enzyme assays showed a good correlation between DIGE-derived protein abundance estimates and enzyme activity in extracts. Overall this study shows that the enhanced drought tolerance of variety Basrah is driven by an enhanced regulation of ROS under drought. A number of transcription factors with enhanced expression in Basrah under drought conditions were also identified; it is hypothesised that these may contribute to the drought tolerant phenotype and thus make interesting targets for barley breeding experiments.
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Janislampi, Kaerlek W. "Effect of Silicon on Plant Growth and Drought Stress Tolerance." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1360.
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Silicon is not considered an essential nutrient, but it is typically abundant in soils and can be taken up in large amounts by plants. Silicon is known to have beneficial effects when added to rice and several other plants. These effects include disease and insect resistance, structural fortification, and regulation of the uptake of other ions. In this study, the effect of silicic acid fertilization on the growth and drought tolerance of four crop plants (corn, wheat, soybean, and rice) was analyzed. Plants were studied using three cultivation techniques: 1) hydroponic solution and subjected to salt stress, 2) low-silicon soil-less medium (peat) and subjected to gradual drought stress, and 3) low-silicon soil-less medium (peat) and subjected to acute drought stress. Silicon was added both as reagent-grade Na2SiO3 and as a siliceous liming agent (PlantTuff). Both forms of Si generally improved drought and salt stress tolerance, but the effects were inconsistent. Silicon increased corn dry mass by up to 18% and the effect was statistically significant (p<0.05) in two out of three techniques. Silicon increased water use efficiency in corn by up to 36% and the effect was statistically significant (p<0.05) in one out of two techniques. In the acute drought stress technique, silicon increased wheat dry mass by 17% and the effect was statistically significant (p<0.05). Silicon increased soybean and rice dry mass by 20 to 30%, but the effect was not statistically significant. Silicon in oldest corn leaves increased from 0.4% to 3% as Si increased from less than 0.01 to 0.8 mM in the hydroponic solution. There was a statistically significant effect of silicon supply on the concentration of some other nutrients, but the effect was often not great enough to be considered biologically important. Rice accumulated the greatest concentration of foliar silicon, corn and wheat were intermediate, and soybean accumulated the least. Collectively, these results indicate an effect of silicon in drought and salinity stress tolerance, but additional studies on the rate and onset of drought are needed to determine interacting factors and better understand the inconsistent results.
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Grossi, D. "ECO-PHYSIOLOGICAL CHARACTERIZATION OF NEW GRAPEVINE ROOTSTOCKS UNDER DROUGHT STRESS." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/253034.
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Extended Abstract
ECO-PHYSIOLOGICAL CHARACTERIZATION OF NEW GRAPEVINE ROOTSTOCKS UNDER DROUGHT STRESS
The objectives of grapevine rootstock breeding selections have undergone a continuous evolution over the years. From the first American vine species introduced to face the invasion of phylloxera and the mildews through Europe, recent breeding programmes aims to obtain plants which are also tolerant to biotic and abiotic stresses such as nematodes, drought and salt stress. Furthermore, the main present interest is on rootstocks that show good performance in different places and in favorable years, but that maintain a good efficiency in difficult conditions. The selection of grapevine rootstocks for resistance to drought conditions is particular important across the activities of modern breeding. Water stress tolerance but above all the water use efficiency (WUE) is becoming more and more important cause the variability of the environmental factors such as limited availability and irregular distribution of water resource. The achievement of the objectives of selection is closely linked to the efficiency and quality of characterization of the phenotype under stress conditions. Traditional phenotyping techniques, although consolidate and widespread, showed considerable limitations like time-consuming and destructive methods. Current technologies allow the development of new systems named high-throughput phenotyping techniques. Thermography, detecting heat patterns in the infrared-wavelength spectrum, is one of the techniques applied in viticulture to assess the plant water conditions.
In addition to phenomics techniques, the detection of changes at the molecular level related to the ability to modify the phenotype under stress also play key roles. The analysis of the changes in gene expression induced by water stress is part of this evolution and the analyses of the transcriptional regulation of some genes involved in the responses to water deficiency shown particular interests.
The present work aims to characterize the eco-physiological responses of new grapevine rootstocks under water stress in comparisons with the most widespread commercial rootstocks and other genotypes of Vitis spp. In particular the study focuses on the strategies in response to water stress and how these modifications can be transmitted to the scion by the rootstock.
The first goal achieved has been the validation of the methods used in high-throughput phenotyping. Thermography has proven a valuable tool in order to assess the water condition of the plant and its evolution during the experiments. The effects of water stress on the variation of stomatal conductance and the rate of growth of the plants have been confirmed allowing the acceleration in phenotyping. It was also possible classify the different behaviors in response to water stress conditions providing a database of phenotypic information to be associated with genotypic data. This point has been particularly important as support to genetic association studies (GWAS) aimed to develop molecular markers to assist and optimize future breeding programs of grapevine rootstock.
Another aspect observed is how the rootstock is able to influence some of the main responses to water stress and how these effects characterize the behavior of grafted variety. In particular several combinations of rootstock with the same scion have been compared: five of the most widespread commercial rootstocks and four new developed rootstocks has been tested under a dry down experiment under controlled greenhouse conditions.
Changes in the eco-physiological status of plants in response to different levels of water stress has been evaluated. The rootstocks have been able to influence the responses to water stress in terms of stomatal conductance (Gs), net photosynthesis (Pn) and stem growth rate (SGR). The modification of gene expression in the roots of the different rootstocks and in the leaves of the scions have also been determined. The differences were observed on transcripts involved in the phenylpropanoid biosynthesis and relative transcription factors involved in the regulation of this pathway, stilbene synthases pathway and on the expression of abscisic acid (ABA) related genes.
The analysis of transcriptional regulation of secondary metabolism has been considered as the main responses involved in the role of protection against oxidative stress induced by drought conditions.
In conclusion, the rootstock has determined a different response according to the genotype but also was able to develop different responses in the scion. This shows that the biosynthetic pathways of ABA, stilbene and flavonoids synthases involved in scion response to drought conditions can be controlled by the rootstock.
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Shawesh, Guimaa Ali 1950. "STOMATAL FREQUENCY IN DROUGHT-TOLERANT AND DROUGHT-SUSCEPTIBLE SORGHUM BICOLOR (L.) MOENCH GENOTYPES GROWN UNDER MOISTURE STRESS AND NONSTRESS." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275503.
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Mardani, Sara, Sayyed Hassan Tabatabaei, Mohammad Pessarakli, and Hamid Zareabyaneh. "Physiological responses of pepper plant (Capsicum annuum L.) to drought stress." Taylor & Francis, 2017. http://hdl.handle.net/10150/626132.
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Water shortage is the most important factor constraining agricultural production all over the
world. New irrigation strategies must be established to use the limited water resources more
efficiently. This study was carried out in a completely randomized design with three replications
under the greenhouse condition at Shahrekord University, Shahrekord, Iran. In this study, the
physiological responses of pepper plant affected by irrigation water were investigated. Irrigation treatments included control (full irrigation level, FI) and three deficit irrigation levels, 80, 60 and 40% of the plant’s water requirement called DI80, DI60, and DI40, respectively. A no plant cover treatment with three replications was also used to measure evaporation from the soil surface.
Daily measurements of volumetric soil moisture (VSM) were made at each 10 cm intervals of
the soil column, considered as a layer. The differences between the measured VSM and the VSM
in the next day and evaporation rate at the soil surface at the same layer of the no plant cover
treatment were calculated. Eventually, by considering the applied and collected water in each
treatment, evapotranspiration (ETC) and root water uptake (RWU) in each layer per day were
estimated. Furthermore, fruit number per plant, fresh fruit weight/day, root fresh/dry weight,
shoot fresh/dry weight, root zone volume, root length and density, crop yield, and water use
efficiency (WUE) were measured under different water treatments. The results showed that the
maximum and minimum of all the studied parameters were found in the FI and DI40 treatments,
respectively. ETC in the DI80, DI60, and DI40 treatments were reduced by 14.2, 37.4, and 52.2%,
respectively. Furthermore, applying 80, 60, and 40% of the plant’s water requirement led to crop yield reduction by 29.4, 52.7, and 69.5%, respectively. The averages of root water uptakes (ARWUs) in the DI80, DI60, and DI40 treatments reduced by 17.08, 48.72, and 68.25%, respectively. WUE and crop yield also showed no significant difference in the FI and DI80 treatments. Moreover, in the DI80 treatment the reduced rate of water uptake was less than the
reduced rate of plant's applied water. According to these results, it can be concluded that 20%
deficit irrigation had no significant reduction on the yield of pepper, but above this threshold,
there was an adverse effect on the growth and yield. Therefore, for water management in the
regions with limited water resources, plant's applied water can be decreased around 20%.
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Velazquez-Mendoza, J. "Studies on the response of Phaseolus vulgaris L. to drought stress." Thesis, Queen's University Belfast, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233263.
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Heinemann, Björn [Verfasser]. "Amino acid metabolism under drought stress in Arabidopsis thaliana / Björn Heinemann." Hannover : Gottfried Wilhelm Leibniz Universität, 2021. http://d-nb.info/1238221696/34.
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Johnson, Stephanie. "The mechanisms of drought stress tolerance in the crop Sorghum bicolor." Thesis, Durham University, 2016. http://etheses.dur.ac.uk/11426/.
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Drought stress can have a major impact upon plant survival and crop productivity. Sorghum bicolor is an important cereal crop grown in the arid and semi-arid regions of >98 different countries. It is well adapted to the harsh drought-prone environments in which it is grown however; relatively few studies have investigated the molecular basis of these adaptations. Breeding programs have lead to the identification of ‘stay-green’ varieties, so-called due to their ability to maintain green photosynthetic leaf area for longer under drought conditions. However, despite extensive breeding efforts to select for this trait we have very little understanding of the fundamental biological processes that underlie it. Microarray analysis was used to identify gene expression changes in sorghum following heat stress, drought stress and combined heat and drought stress. These microarrays were additionally used to compare gene expression in stay-green (drought-tolerant) and senescent (drought-sensitive) sorghum lines. Ontological analysis of the genes expressed to higher levels in the stay-green lines identified key processes hypothesised to be associated with the trait. These include genes associated with proline and betaine biosynthesis, glutathione S-transferase (GST) activity and the regulation of stomatal aperture and density. Both proline levels and GST activity were found to be higher in the stay-green lines thus validating that the changes at the gene expression level result in changes at the protein level. Stay-green lines were also shown to have reduced transpiration and reduced numbers of stomata. Two signalling genes, DREB1A and SDIR1 were expressed to higher levels in the stay-green varieties. Transgenic lines overexpressing these genes were generated in order to test their function. Based on the gene expression data, putative mechanisms underlying two QTL for the stay-green trait (Stg1 and StgB) were generated. Further validation of these genes and processes could not only improve our understanding of drought tolerance mechanisms in sorghum, but also facilitate the improvement of future sorghum cultivars.
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Hodecker, Bárbara Elias Reis. "Comparison of drought stress responses of tolerant and sensitive eucalypt genotypes." Universidade Federal de Viçosa, 2015. http://www.locus.ufv.br/handle/123456789/6511.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Para lidar com a restrição hídrica, seleções de genótipos tolerantes à seca tem sido umas das principais estratégias adotadas nos novos plantios. Entretanto, no Brasil, a maioria das seleções genéticas tem focado principalmente nas taxa de crescimento e produtividade das fibras, sem levar em consideração o melhor entendimento das respostas morfológicas e bioquímicas em resposta ao déficit hídrico e também a influência dos nutrientes nestes processos. Assim, os principais objetivos foram comparar as respostas de clones tolerantes e sensíveis de eucalipto frente ao déficit hídrico a fim de auxiliar no entendimento destas características e futuras seleções genéticas para esta espécie. Outro objetivo visou identificar a importância da fertilização com B (boro) nos mecanismos adaptativos relacionados à tolerância à seca e o melhor entendimento das relações envolvendo a eficiência nutricional em diferentes materiais genéticos e sua influência na seleção de genótipos tolerantes, utilizando para este fim, os diagramas nutricionais. Para atingir estes objetivos, foram conduzidos quatro experimentos, sendo três deles em casa de vegetação e um em condições de campo. O objetivo do primeiro experimento foi avaliar a influência da nutrição com boro em processos relacionados à eficiência do uso da água em seis espécies de eucalipto oriundas de diferentes condições edafoclimáticas e submetidas à seca. O segundo experimento foi destinado à identificação das alterações morfológicas, fisiológicas e moleculares causadas após longo período de restrição hídrica, em quatro espécies de eucalipto em condições de campo. O objetivo do terceiro experimento foi avaliar as variáveis capazes de discriminar clones com tolerância diferencial ao estresse hídrico e fornecer marcadores para plantas jovens de eucalipto. O quarto experimento objetivou avaliar o comportamento diferencial no crescimento inicial e eficiência nutricional e da água em dez clones de eucaliptos submetidos à restrição hídrica. No primeiro capítulo, observamos elevado incremento na eficiência do uso da água em plantas sob seca e suplementadas com B, devido à combinação de alta taxa fotossintética, alta concentração de K+ em folhas, promovendo maior fechamento estomático, menor perda de água e maior translocação de açúcares para o crescimento radicular. No experimento de campo (capítulo 2), os resultados obtidos sugerem que árvores de eucalipto crescendo sob uniforme e elevada precipitação anual mostraram se mais estressadas após longo período de déficit hídrico, comparado às árvores submetidas à períodos de estresse hídricos recorrentes. No capítulo 3, não foi possível identificar uma variável capaz de discriminar e agrupar clones de eucalipto com tolerância diferencial ao estresse hídrico, no entanto, a interação entre eficiência do uso da água, ABA, fotossíntese, transpiração e razão massa de matéria seca parte área e massa de matéria seca radicular mostraram ser importantes diferenças entre materiais genéticos. De maneira interessante, os resultados obtidos nos capítulo 4, mostram que sob estresse hídrico, clones tolerantes geralmente apresentam maior eficiência de absorção (AE), mas menor eficiência de uso (UE) de nutrientes, enquanto, clones sensíveis tiveram baixa AE, baixa UE para formação de raízes e alta AE para formação de folhas.
To cope with water restriction, the selection of drought tolerant genotypes has been the main strategy being adopted to establish new plantings. However, in Brazil, most genetic selections have focused mainly on growth rates and fiber productivity, without a clear understanding of morphological and biochemical responses of trees to water stress and the influence of nutrients on these processes. Thus, the main goals of this thesis were to compare water stress responses of tolerant and sensitive Eucalyptus genotypes in order to help to understand of Eucalyptus drought tolerance traits and assist future Eucalyptus breeding programs. Another objective was to identify the nutritional influence of B (boron) on water stress adaptive mechanisms and understand the relationship between nutritional efficiency and its influence on tolerant genotype selections using nutritional diagrams. In order to achieve these proposals, we conducted four experiments, three under controlled conditions and one under field conditions. The objective of the first experiment was to evaluate the influence of B nutrition on physiological processes related to water use efficiency in six Eucalyptus species of contrasting ecotypes under water stress. The second experiment was designed to identify the morphological, physiological and molecular changes caused by long periods of water restriction in four Eucalyptus clones under field conditions. The objective of the third experiment was to identify variables able to discriminate and group clones with differential tolerance to water stress and provide markers for young plants of eucalypt. The fourth experiment aimed to evaluate the differential behavior in the initial growth, biomass accumulation, and nutritional efficiency and water use in 10 Eucalyptus clones submitted to water stress. In the first chapter, we observed a strong increment on instantaneous WUE (water use efficiency) in D+B (drought and B supply) plants, due to the combination of higher photosynthetic rate, higher K+ concentration in leaves promoting higher stomatal closure, lower water loss and a higher translocation of sugars and B to root growth. In our field experiment (chapter 2), our results suggest that trees growing in the area with uniform annual high precipitation showed were stressed after a long period of drought, compared to those stands submitted to annual water-stress fluctuation period. In the chapter 3, we could not identify one single variable able to discriminate and group clones with differential tolerance to water stress, however, the interaction between WUEg (water use efficiency), ABA, A (photosynthesis), E (transpiration) and SDM/RDM (shoot dry matter/root dry matter) seemed to be the most important differences between clones under water stress. Our results from chapter 4, interestingly showed us that under water stress the drought-tolerant clone generally had high AE (absorption efficiency), but low nutrient UE (use efficiency), whereas the sensitive clone had low AE, low UE for root formation and high AE for leaf formation.
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Carroll, David A. "Drought and Nitrogen Effects on Maize Canopy Temperature and Stress Indices." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5932.
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Increased water scarcity due to changing climate, population growth, and economic development is a major threat to the sustainability of irrigated agriculture in the Western United States and other regions around the world. Management practices, such as controlled deficit irrigation, that seek to maximize the productivity of a limited water supply are critical. When using controlled deficit irrigation, remote sensing of crop canopy temperature is a useful tool for assessing crop water status and for more precise irrigation management. However, there is potential that nutrient deficiencies could compound the interpretation of water status from leaf temperature by altering leaf color and radiation balance. One objective of this thesis was to evaluate whether nitrogen fertility status of maize interacts with remotely sensed leaf temperature under full and limited irrigation. Another objective was to evaluate the effect of varying irrigation and nitrogen regimes on three water stress indices: Crop Water Stress Index (CWSI), Degrees Above Non-Stressed (DANS), and Degrees Above Canopy Threshold (DACT). Replicated studies were conducted using maize grown in both the glasshouse and the field. The glasshouse study consisted of combinations of well-watered and drought irrigation and sufficient and deficient nitrogen levels, while the field study consisted of combinations of well-watered, limited or controlled deficit, and drought irrigation and sufficient, sufficient delayed, and deficient nitrogen levels. In the glasshouse, leaf chlorophyll content was reduced moderately by limited irrigation and more so by N deficiency. For most observations in the glasshouse, the remotely sensed leaf temperatures were affected by irrigation, but not by N level. With drought irrigation, leaf temperature averaged 29.0° C, compared to 27.9 °C for the well-watered treatment. Similar results were observed in the field, illustrating the utility of canopy temperature in detecting water stress and that the measurement was not confounded by N status. It was also found that irrigation had a significant effect on all three water stress indices. For example, in the glasshouse, cumulative DANS was 32.2 for the drought treatment and 15.5 for the well-watered treatment. Similar results were found for other stress index measurements both in the glasshouse and the field. DANS underestimated stress on days when the reference crop was stressed and overestimated stress on low temperature days. DACT risks finding no stress when temperatures are below the canopy threshold temperature of 28.0 °C. Thus, CWSI is the most effective index, given that it takes humidity and air temperature into account. Indices were only weakly related to leaf area, biomass or grain yield, or crop water productivity. Linear regression of Nitrogen Sufficiency Index and its effect on crop growth found significant effects on biomass and grain yield, crop water productivity, and final leaf area. Thus, water stress indices are useful tools in evaluating crop water status, but consideration of other factors, such as nutrient status, must be taken for prediction of crop growth and yield.
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Gokcay, Derya. "Physiological And Biochemical Screening Of Different Turkish Lentil (lens Culinaris M.) Cultivars Under Drought Stress Condition." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615008/index.pdf.
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Legumes being the most important crops worldwide are limited in terms of adaptability and productivity mainly by the abiotic stresses. In this study, the aim was to understand tolerance mechanisms of lentil cultivars under drought stress by physiological and biochemical analyses. This study was carried out with six Turkish Lentil cultivars (Seyran, Kafkas, Malazgirt, Çagil, Ç
iftç
i, Ö
zbek) subjected to drought stresses (10% and 15% PEG) and their physiological and biochemical properties were examined to select drought-tolerant and drought-sensitive cultivars. Drought stress was applied for 5 days to 7 days-grown lentil plants. 12-days old, stressed and control plant shoots and roots were analyzed in terms of physiological and biochemical parameters (length, fresh weight, ion leakage, proline, MDA and H
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[Verfasser], Setegn Gebeyehu. "Physiological response to drought stress of common bean (Phaseolus vulgaris L.) genotypes differing in drought resistance / vorgelegt von Setegn Gebeyehu." Göttingen : Cuvillier, 2006. http://d-nb.info/988661039/34.
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Mallah, Abdul Nabi. "Effects of water stress and salinity on contrasting wheat genotypes." Thesis, Bangor University, 1991. https://research.bangor.ac.uk/portal/en/theses/effects-of-water-stress-and-salinity-on-contrasting-wheat-genotypes(d16c3b0e-d0a0-44e3-ada1-79fce0bd31ce).html.
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A series of experiments was carried out in the Department of Agriculture, University College of North Wales, Bangor, during October 1987 to September 1989. The purpose of these was to study the effects of water stress and salinity stress at different stages on long (Norman), medium (Fenman) and short duration (Wembley) wheat varieties in different environments. Effects of water stress were tested in large pots in different types of soil. Effects of salinity were tested by growing plants in solution culture. In both experiments water stress and salinity stress were imposed at three major stages, tillering to stem extension (TL-SE), stem extension to booting (SE-BG) and booting to maturity (BG-MT). These were tested in each variety in comparison with a control of each variety. Growth measurements, leaf number and area, stem area, shoot number, plant height, nitrogen %, nitrogen uptake, dry weight per plant were determined at the end of each stage. Soluble carbohydrates were determined at anthesis. This was done to find out how much these growth measurements were decreased during each stress period. Yield and yield components were determined at harvest. In these experiments the long duration variety took a long time in growth during TL-SE, in comparison to mid winter and spring wheat varieties. The long duration variety gave a higher plant, more straw dry weight production and more leaf number than the short duration variety. The long duration variety also gave a higher yield than the medium and short duration varieties, due to larger ears, more spikelets vi per ear, more grain number per ear and more grain number per spikelet. All varieties experienced higher temperatures and longer days during SE-BG and BG-MT in both experiments. The lengths of these stages therefore showed smaller variation between varieties. In water stress experiments the mixed peat-soil used in Experiment 2 dried out quicker than the normal field soil used in Experiment 1. The upper portion of the soil was dried before the lower portion of the soil during the stress period. With water stress at SE-BG and BG-MT the soil dried out quicker in both years. Gypsum blocks were used to give readings of water stress. with water stress at BG-MT the soil was completely dried out after the third week, in all varieties, due to higher plant height, higher temperature and more evaporation. Because of this water stress at BG-MT resulted in a short duration for ripening. In both water stress Experiments 1 and 2, in all varieties all water stress treatments decreased the growth measurements, decreased yield and yield components. In Norman water stress at TL-SE had a long stress period due to slow growth processes during cold winter. However, this stage had a similar effect on yield in Norman, Fenman and Wembley. In both water stress experiments in all varieties, water stress at SE-BG caused the largest reductions in growth measurements, because at this stage the plant had the greatest leaf area and temperature was higher, although the period of stress was only a few weeks. However, water stress at BG-MT caused the greatest decreases in yield. This stage showed the greatest vii decreases in yield and yield components, due to small grain size, fewer fertile spikelets, small size of ear, earlier leaf senescence, short duration for ripening, higher temperature, lack of soluble carbohydrate for grain f~lling from stem and pollination problems at anthesis time. In both salinity Experiments 1 and 2, all varieties had a larger green leaf area, more tillers and all varieties were much stronger after stem extension than in the water stress experiments due to the solution culture teChnique. Norman was more strong than the other varieties because of its long period grown in solution culture. Salinity at TL-SE was more damaging than other stages in all varieties. Salinity at TL-SE decreased the growth measurements, such as leaf area, stem area, plant height, dry weight per plant. Because of the growth measurement reduction, grain weight per plant, grain number per plant, grain number per ear, grain number per fertile spikelet and fertile spikelet per ear were decreased by salinity at this stage. Salinity at SE-BG and BG-MT also decreased growth measurements, decreased grain yield and yield components. Salinity at BG-MT decreased grain yield and yield components more than salinity at SE-BG. In Experiment 2 in all varieties with salinity at BG-MT plants were harvested a few days before other stages and the control. Norman was more sensitive with salinity at TL-SE than the other varieties because of its long period grown under salt stress. Norman was much stronger with salinity at SE-BG. Norman gave lower yield, yield components at BG-MT than other varieties at this stage.
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Green, Andrew Justin. "Abiotic stress tolerance from the tertiary gene pool of common wheat." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/32746.
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Doctor of PhilosophyDepartment of Agronomy
Allan K. Fritz
Heat and drought stress are two of the most significant abiotic stresses limiting wheat production in the Great Plains and worldwide. Introgression of novel tolerance genes from wild relatives is a strategy which presents promise. This study examined both heat and drought tolerance from the tetraploid species Aegilops geniculata (U[superscript g]U[superscript g]M[superscript g]M[superscript g]). Additional screening for heat tolerance was conducted with the US genome species Aegilops peregrina (Hack) and Aegilops kotschyi (Boiss). A comprehensive screening system for drought tolerance was also constructed to evaluate wheat and its wild relatives. Previous reports suggested that Ae. geniculata accession TA2899 was moderately tolerant to heat stress. It had also previously been used to develop a full set of wheat-Ae. geniculata chromosome addition lines in a Chinese Spring background. To identify the chromosome(s) carrying the heat tolerance, all addition lines, as well as wheat check genotypes, were screened for post-anthesis heat tolerance in two growth chamber experiments. No chromosome addition lines were significantly different (p<0.05) from Chinese Spring, and none were found to have superior performance to the positive check cultivars. Forty-five accessions of Ae. peregrina and its close relative, Ae. kotschyi were screened in a post-anthesis heat experiment. A follow-up experiment compared the genotypes in a split-plot temperature treatment with heat and optimal growth chambers. Many accessions were similar to the control genotypes for grain fill duration, and some exceeded the wheat controls for relative chlorophyll index values on Day 12 and Day 16. TA1889 and TA1904, both Ae. peregrina accessions originating from Israel, had a higher grain fill duration across experiments than the best wheat control, and warrant further investigation. Previous reports suggested drought tolerance in Ae. geniculata. After preliminary screenings, six genotypes were selected for advanced screening and compared with three wheat cultivars. The advanced greenhouse screening system was conducted in 152cm tall PVC growth tubes. The experiment measured multiple plant responses, and had a datalogging system automatically collecting water content and matric potential of the growth media. Multiple accessions warranted further investigation, and showed potentially different modes of drought tolerance, with varying levels of stomatal resistance, biomass, and osmotic adjustment.
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Yang, Yang. "Non-contacting techniques for detecting plant drought stress in a closed environment." Connect to this title online, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1068499233.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xx, 245 p.; also includes graphics. Includes bibliographical references (p. 206-216).
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Fidelibus, Matthew, Chris Martin, and Jean Stutz. "Contributions of Beneficial Soil Fungi to Drought Stress Tolerance of Young Citrus." College of Agriculture, University of Arizona (Tucson, AZ), 1997. http://hdl.handle.net/10150/220566.
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Four arbuscular mycorrhizal (AM) fungal isolates (Glomus sp.) from disparate edaphic conditions were screened for effects on whole -plant transpiration of juvenile 'Volkamer' lemon (Citrus volkameriana Ten. and Pasq.) plants of similar shoot mass and canopy leaf area. Mycorrhizal and non -mycorrhizal plants were grown in 8 -liter containers for 2.5 months under well- watered conditions before subjection to three consecutive soil drying episodes of increased severity (soil moisture tensions of -0.02 [still moist], -0.06 [moderately dry], and -0.08[dry] MPa respectively). Whole plant transpiration measurements were made on the last day of each soil drying episode and measurements were repeated on the first and second days after re- watering, when soil profiles were moist. The percent root length colonized by AM fungi differed among isolates. Three AM fungal isolates, Glomus sp. 25A, Glomus mosseae (Nicol. & Gerde.) Gerde. & Trappe 114C, and Glomus intraradices Schenck & Smith FL 208-3 increased root length and subsequently increased lemon plant water use. Conversely, plants inoculated with Glomus mosseae 51C did not enhance lemon plant root length nor improve plant water use compared with nonmycorrhizal control plants. Inoculating citrus with AM fungi that promote root extension may reduce plant water deficit stress under field conditions.
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Scott, Lance V. "Precision Drought Stress in Orchards: Rootstock Evaluation, Trunk Hydration and Canopy Temperature." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/5407.
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In many areas, over half of all diverted water is used for irrigation. Tree fruit crops use a lot of water, but water productivity can be increased using properly-timed precision water stress. In addition to water conservation, increases in water productivity arise from better fruit quality, increased storage life and reductions in pruning and maintenance. One major hurdle to applying precision water stress in orchards is the lack of a reliable, automated method of determining tree water status. However, the influence of physiological characteristics such as rootstock vigor on water productivity are also important. Selecting the most appropriate rootstocks and accurately determining the water status of orchard trees can increase water productivity.
Research has shown that some rootstocks can more effectively extract water from soil. In this research, the response to water stress of three different Gisela tart cherry dwarfing rootstocks was compared using a weighing lysimeter system. Gisela 12 and Gisela 3 rootstocks recovered from drought stress more quickly and had higher trunk diameter growth rates than drought-stressed Gisela 5 rootstocks.
Two potential methods of determining tree water status were also evaluated. Trunk hydration was measured using electromagnetic sensors and canopy temperature changes were detected using infrared radiometry.
Electromagnetic techniques, including time domain reflectometry, can be used to determine the water content of wood. Until recently, the cost of this technology has inhibited its widespread use, but new affordable commercial electromagnetic soil moisture sensors have created renewed interest in this technique. In this research five different types of electromagnetic soil moisture sensors were inserted into the trunks of fruit trees and were monitored over two growing seasons. Maximizing exposure of waveguides to the sapwood increased the response of these sensors to changes in stem water potential.
Infrared measurements of canopy temperature have successfully been used with field crops. However, the heterogeneity of orchard canopies makes this technique more difficult in orchards. Here, the efficacy of aiming radiometers at single trees versus at entire orchards was compared over multiple growing seasons. Neither single tree measurements nor whole orchard techniques produced a sufficiently robust signal to recommend them for general use.
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Wang, Lijun. "Physiological response of Kentucky bluegrass under salinity stress." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1492.
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Salinity is a major abiotic stress in plant agriculture which reduces seed germination, vegetative growth, and flowering, and limits crop productivity world-wide. Salinity causes water deficit, ion toxicity, and nutrient deficiency in plants, which can result in cellular damage, growth reduction, and even death. Kentucky bluegrass (Poa pratensis L.) is the most widely used cool-season species in cool-arid climates; however it has relatively poor salt-tolerance. Thus the development of Kentucky bluegrass genotypes with increased salt tolerance is of interest to turf breeders. One impediment to selection towards this goal is finding an efficient and accurate method to evaluate the salt tolerance. The objective of this study was to examine physiological responses to salt stress and to evaluate the genetic diversity among the accessions used in the research. Salt-tolerant accessions PI371768 (768) and PI440603 (603) and salt-sensitive varieties Midnight and Baron were exposed to four levels of salinity imposed by irrigating with salt solutions of 0 dS m-1 (control), 6 dS m-1, 12 dS m-1, and 18 dS m-1 or 24 dS m-1. Soil salinity was measured using Acclima Digital TDT sensors and grass response to the stress was measured using turf quality ratings, stomatal conductance, leaf water potential and electrolyte leakage. In general, turfgrass quality, stomatal conductance, and leaf water potential decreased while electrolyte leakage increased under salinity stress. Midnight and Baron exhibited greater changes in these measurements, indicating more sensitivity compared to 768 and 603. The 6 dS m-1 treatment had little effect on the salt-tolerant accessions. Salt tolerance of 603 and 768 was confirmed and likewise, salt sensitivity of Baron and Midnight was confirmed. The genetic similarity of all cultivars used in this study was very high.
All of the evaluation measurements were highly correlated, with water potential and electrolyte leakage being the most reliable and accurate methods due to the low standard deviations. Due to more repeatable methods and less user error, electrolyte leakage and turfgrass quality are recommended methods for screening salt tolerance of turfgrasses.
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Cook, Ritchard Matthew. "Changes in gene expression in response to abscisic acid and environmental stress." Thesis, University of the West of England, Bristol, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293362.
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O'Neill, Michelle. "A role for lipoxygenase in stress responses in Pisum sativum L." Thesis, University of East Anglia, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389268.
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Sewpersad, Chandani. "The development, validation and implementation of a drought stress index for the evaluation of the drought tolerance potential of South African sugarcane." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/79823.
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Thesis (MSc)--Stellenbosch University, 2013.ENGLISH ABSTRACT: In the rainfed areas of the South African sugar industry the unpredictability of rainfall is of major concern for producers. Currently, research into the drought tolerance of South African sugarcane varieties is very limited. Knowledge of varietal drought tolerance potential would allow for more informed decision making when it comes to planting a crop that stays in the ground for between five and fifteen years. The aim of this study was to ascertain the drought tolerance potential of commercial sugarcane varieties using historical field trial data by employing statistical modelling. The first step was to establish a reliable methodology of quantifying the level of drought stress, defined through a drought stress index (DSI), employing the sugarcane growth modelling software Canesim. The second step was to use the selected DSI to evaluate and rate the drought tolerance potential of commercial varieties. Of the six DSI’s calculated, the index comprising a ratio of Canesim simulated rainfed yield (representative of a water stressed environment) to Canesim simulated irrigated yield (representative of a water unstressed environment) was the best at quantifyingthe level of trial drought stress. Using three varieties with previously identified drought potential, two intermediate susceptible (IS) and one intermediate (I) variety, this was the only DSI that was able to quantify all the differences between the varieties. Using the selected DSI, two different methodologies were used to evaluate varietal drought tolerance potential: General linear regression and Residual maximum likelihood meta-analysis. The regression method proved to be a better method of varietal rating when using historical field data. The two rainfed regions, coastal and midlands were analyzed separately due to the difference in climatic conditions. Using the regression analysis, with N12 as the observed intermediate reference variety, coastal varieties were rated as being susceptible (N16, N19, N39 and NCO376) or intermediate (N27, N29, N33, N36, N41, N45, N47). Rating of the midlands varieties, with both statistical methods, were unsuccessful.
AFRIKAANSE OPSOMMING: Binne die droëland produksiegebied van die Suid-Afrikaanse suikerindustrie is die wisselvalligheid van reënval ʼn groot bron van kommer vir produsente. Navorsingsresultate aangaande die droogtetoleransie van Suid-Afrikaanse suikerrietvariëteite is baie beperk. Aangesien suikerriet aanplantings vir vyf tot vyftien jaar in produksie mag bly, is kennis aangaande droogtetoleransie noodsaaklik vir ingeligte besluite rondom variëteit keuse. Die doel van hierdie studie was om die droogtetoleransie van kommersiële variëteite met behulp van historiese veldproef resultate en statistiese modellering te bepaal. Die eerste stap was die ontwikkeling van betroubare metodiek wat die graad van droogtestremming kwantifiseer deur middel van droogtestremmingsindekse (DSI’s) wat met die suikerriet produksiemodel, Canesim, bereken is. Die tweede stap was om die DSI’s te gebruik om geselekteerde kommersiële variëteite vir droogtetoleransie te evalueer en volgens toleransie te rangskik. Van die ses DSI’s wat geëvalueer is, was die indeks wat die verhouding tussen Canesim gesimuleerde droëland opbrengs (verteenwoordigend van ʼn omgewing met droogte) en Canesim gesimuleerde besproeide opbrengs (verteenwoordigend van ʼn omgewing sonder droogte) omskryf het, die mees effektiefste om die graad van droogtestremming te kwantifiseer. Hierdie DSI was vervolgens die enigste wat verskille in droogtetoleransie tussen drie variëteite van bekende droogte toleransie kon kwantifiseer. Deur gebruik van hierdie DSI is twee verskillende metodes aangewend om die droogtetoleransie van variëteite te evalueer naamlik: Algemene Lineêre Regressie en Residuele Maksimum Aanneemlikheid. Die regressiemetode was die mees effektiefste om variëteite volgens droogtetoleransie, op grond van historiese veldproef resultate, te rangskik. Die twee droëland produksiegebiede, naamlik die kusstrook en Natalse Middellande is afsonderlik geanaliseer as gevolg van klimaatsverskille. Met behulp van die regressiemetode is die kus-variëteite as droogtesensitief of -intermediêr geklassifiseer, met N27, N29, N33, N36, N41, N45 en N47 as droogte-intermediêr en N16, N19, N39 en NCO376 as droogtesensitief. Soortgelyke klassifisering van die variëteite wat in die Natalse Middellande verbou word was nie met enige van die statistiese metodes suksesvol gewees nie.
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Shroyer, Kyle J. "The effects of drought and high temperature stress on reproduction, physiology, and yield of spring and winter wheat." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/34542.
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Doctor of PhilosophyDepartment of Agronomy
P. V. Vara Prasad
Drought and high temperature are major detriments to global wheat production. Wheat varies in its susceptibility to drought and high temperature stress. Three experiments were performed to address the challenges of drought and high temperature stress in wheat. The first experiment consisted of 256 genotypes of spring wheat and 301 genotypes of winter wheat, field screened for yield traits related to drought tolerance, in irrigated and dryland experiments. The experimental designs for the first experiment were both augmented incomplete block designs with one-way or row-column blocking. This experiment was performed at the Ashland Bottom Research Farm, south of Manhattan, KS, between 2011-2013. From this experiment, three conclusions were made: wheat genotypes vary widely in their responses between dryland and irrigated treatments and this variation can be used in future experiments or breeding tolerant genotypes. The number of seeds per unit of area, total biomass per unit area, and the average weight of one thousand seeds, were the best yield traits for predicting yield in both irrigated and dryland environments. Twenty genotypes were selected for future research based on their susceptibility or tolerance to drought. The second experiment was performed in the greenhouse facilities to observe the source-sink relationship of spring wheat genotype Seri 82 under drought and defoliation. The experiment was a randomized complete block design with a split-plot treatment arrangement. Post-anthesis cessation of watering and defoliation were the treatments. Both water stress and defoliation affected seed yield and total biomass. The major effect of post-anthesis water stress was a decrease in single seed weight. Defoliation affected the source-sink relationship by reducing the source strength of the leaves. This caused the stem to contribute more to overall yield. The defoliation also caused the remaining leaves to compensate for the removed leaves. The final experiment evaluated the changes in seed-filling rate and duration of three winter wheat genotypes during high temperature stress. High temperature stress reduced the duration of seed fill and increased the rate, differently in each genotype. Higher yields in the winter wheat growing regions, susceptible to post-anthesis high temperature stress, may be possible through selection of cultivars with faster seed-filling rates and/or duration of seed filling.
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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.
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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.Master of Science
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Nkomo, Mbukeni Andrew. "Comparative analysis of molecular and physiological responses of two canola genotypes to drought stress." Thesis, University of the Western Cape, 2016. http://hdl.handle.net/11394/5298.
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>Magister Scientiae - MScFood security has always been one of the priority concerns in Africa, and it is mostly threatened by drought stress due to climate change. Drought-induced stress is one of the serious limiting factors of plant production, and it is known to impose oxidative stress as a consequence of excessive reactive oxygen species (ROS) accumulation that lead to lipid peroxidation, which is manifested as increased cell death. Hence, this study investigated the influence of drought stress on two contrasting canola genotypes (Agamax and Garnet), by monitoring their physiological and molecular changes. The results showed that the plant growth and biomass of both genotypes were significantly affected by drought stress as a consequence of excessive ROS accumulation (manifested as H₂O₂ and OH· content). However, under drought stress conditions, the reduction in biomass and shoot length was more pronounced in the Garnet genotype when compared to that of the Agamax genotype. This was further supported by the increase in lipid peroxidation and cell death, which were shown to be significantly higher in the Garnet genotype when compared to the Agamax genotype under drought stress. ROS scavenging ability which prevents oxidative stress and ultimately ROS-induced cellular damage. Hence, given the higher levels of antioxidant activity coupled with the reduction in ROS accumulation that was observed in the Agamax genotype, we suggest that the Agamax genotype might be slightly less susceptible to drought stress, when compared to the Garnet genotype. Furthermore, understanding the proteomic responses of these two contrasting genotypes that showed a marked difference in response to drought stress might help in unlocking complex biological networks of proteins underlying drought stress tolerance. Hence we use two-dimensional (2D) gel electrophoresis coupled with Matrix assisted laser desorption/ionisation-time of flight/time of flight tandem mass spectrometry (MALDI TOFTOF MS) analysis for this part of the study, in order to detect and analyze those differentially expressed proteins or proteins whose abundance levels were influenced as a consequence of drought stress. To gain additional insight into the leaf proteomes of the two canola genotypes, a protamine sulphate precipitation (PSP) method was used to remove RuBisCo and confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis. A total of 55 well resolved protein spots were selected for mass spectrometry analysis of which 31 (56%) were positively identified using the selective criteria analysis (SCA). All positively identified proteins were then classified into functional categories including protein folding (3%), photosynthetic (29%), detoxification and protection (20%), and energy related proteins whereas 16% could not be classified into any functional category. Apart from spot 32 (Fe superoxide dismutase) and spot 34 (chloroplast beta-carbonic anhydrase), no further significant difference in protein expression/abundance was observed for all the identified proteins for both genotypes in response to drought stress. Both proteins (spots 32 and 34) have been shown to contain antioxidant activity properties which suggest that they might play a crucial role in improving drought stress tolerance in canola plants.
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BERGONTI, MAURO. "PHYSIOLOGICAL AND MOLECULAR ANALYSIS OF DROUGHT RESPONSE IN SWEET SORGHUM." Doctoral thesis, Università Cattolica del Sacro Cuore, 2013. http://hdl.handle.net/10280/1745.
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Il sorgo zuccherino utilizzato per produrre cibo, mangimi e carburante con limitato impiego di risorse, risponde ai criteri dell’agricoltura moderna ed è impiegato nella produzione di bioenergia. È una pianta C4 adattata agli ambienti semi-aridi, caratteristica che dovrebbe essere mantenuta e migliorata nel processo di ottenimento di nuovi genotipi. Per comprendere le basi genetiche e fisiologiche della tolleranza alla siccità, genotipi di sorgo (IS 19453, Mpwekwa, SDS19483, IS33350, BR505, BR501) sono stati valutati in camera di crescita e in serra. Lo stress idrico è iniziato quando le piante avevano consumato l'80% di acqua disponibile. L’RNA totale è stato estratto da piante irrigate e non a diversi livelli di stress idrico. L'analisi di espressione genica è stata eseguita attraverso l’uso delle tecniche microarray e q-RT PCR. Il numero dei geni differenzialmente espressi aumentava all’aumentare del livello di stress. Gran parte dei geni sovra espressi erano coinvolti nei meccanismi di difesa, di trasporto, di regolazione genica, e nel metabolismo lipidico, proteico e degli zuccheri. Nelle piante non irrigate, al più alto livello di stress, i geni sovra-regolati presentavano livelli di espressione di 2-5 volte superiori rispetto ai campioni di controllo. Questi risultati serviranno all’identificazione di ”single nucleotide polymorphisms” nelle sequenze dei geni candidati e al loro impiego come marcatori nel processo di miglioramento genetico assistito.Sweet sorghum providing food, feed and fuel with a limited use of resources, responds to the criteria of sustainable bioenergy production. Sorghum is a C4 plant adapted to semi-arid environments, characteristic that should be maintained and further improved in the process of breding new genotypes for bioenergy production. To understand the genetic and physiological basis of drought tolerance, sorghum genotypes (IS 19453, Mpwekwa, SDS19483, IS33350, BR505, BR501) were evaluated in growth chamber and greenhouse experiments. Drought stress started when plants had consumed 80% of transpirable soil water. Total RNA was extracted from irrigated and not irrigated plants at different levels of water stress, and gene expression analysis was carried out using microarray and q-RT PCR techniques. The number of differentially expressed genes increased with the stress level. Most of the up regulated genes were involved in cell rescue, transport, nucleic acid binding, and in lipid, protein and sugar metabolism. In non-irrigated plants, at the higher stress level, up-regulated genes presented levels of expression 2-5 fold higher compared to control samples. These preliminary results will be useful for the identification of single nucleotide polymorphisms in candidate genes sequences in order to use them as markers for assisted breeding.
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BERGONTI, MAURO. "PHYSIOLOGICAL AND MOLECULAR ANALYSIS OF DROUGHT RESPONSE IN SWEET SORGHUM." Doctoral thesis, Università Cattolica del Sacro Cuore, 2013. http://hdl.handle.net/10280/1745.
Full textAbstract:
Il sorgo zuccherino utilizzato per produrre cibo, mangimi e carburante con limitato impiego di risorse, risponde ai criteri dell’agricoltura moderna ed è impiegato nella produzione di bioenergia. È una pianta C4 adattata agli ambienti semi-aridi, caratteristica che dovrebbe essere mantenuta e migliorata nel processo di ottenimento di nuovi genotipi. Per comprendere le basi genetiche e fisiologiche della tolleranza alla siccità, genotipi di sorgo (IS 19453, Mpwekwa, SDS19483, IS33350, BR505, BR501) sono stati valutati in camera di crescita e in serra. Lo stress idrico è iniziato quando le piante avevano consumato l'80% di acqua disponibile. L’RNA totale è stato estratto da piante irrigate e non a diversi livelli di stress idrico. L'analisi di espressione genica è stata eseguita attraverso l’uso delle tecniche microarray e q-RT PCR. Il numero dei geni differenzialmente espressi aumentava all’aumentare del livello di stress. Gran parte dei geni sovra espressi erano coinvolti nei meccanismi di difesa, di trasporto, di regolazione genica, e nel metabolismo lipidico, proteico e degli zuccheri. Nelle piante non irrigate, al più alto livello di stress, i geni sovra-regolati presentavano livelli di espressione di 2-5 volte superiori rispetto ai campioni di controllo. Questi risultati serviranno all’identificazione di ”single nucleotide polymorphisms” nelle sequenze dei geni candidati e al loro impiego come marcatori nel processo di miglioramento genetico assistito.Sweet sorghum providing food, feed and fuel with a limited use of resources, responds to the criteria of sustainable bioenergy production. Sorghum is a C4 plant adapted to semi-arid environments, characteristic that should be maintained and further improved in the process of breding new genotypes for bioenergy production. To understand the genetic and physiological basis of drought tolerance, sorghum genotypes (IS 19453, Mpwekwa, SDS19483, IS33350, BR505, BR501) were evaluated in growth chamber and greenhouse experiments. Drought stress started when plants had consumed 80% of transpirable soil water. Total RNA was extracted from irrigated and not irrigated plants at different levels of water stress, and gene expression analysis was carried out using microarray and q-RT PCR techniques. The number of differentially expressed genes increased with the stress level. Most of the up regulated genes were involved in cell rescue, transport, nucleic acid binding, and in lipid, protein and sugar metabolism. In non-irrigated plants, at the higher stress level, up-regulated genes presented levels of expression 2-5 fold higher compared to control samples. These preliminary results will be useful for the identification of single nucleotide polymorphisms in candidate genes sequences in order to use them as markers for assisted breeding.
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Nájar, Durán Elena. "Characterization of the maize protein ZmSTOP1 and its role in drought stress response." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/327875.
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El déficit hídrico se ha convertido un una gran amenaza hacia la producción agrícola en todo el mundo. La identificación de nuevos actores en la respuesta al estrés por sequía en plantas cultivables es vital para entender su adaptación a crecientes cambios ambientales.
El ácido abscísico (ABA) es una hormona vegetal que media las respuestas adaptativas a la sequía, como la dormancia de semillas, el cierre estomático y la detención del crecimiento de la raíz. En el caso de la regulación estomática, el ABA activa la quinasa OST1, que a su vez fosforila diferentes sustratos, por ejemplo NADPH oxidasas, canales iónicos y factores de transcripción, lo que al final conducirá al cierre estomático. Aunque el cierre estomático en respuesta a ABA es esencial para evitar la desecación y, por lo tanto, la muerte de la planta, se debe mantener un cierto nivel de conductividad estomática para permitir el intercambio de gases y la transpiración, esencial para la captación de agua y solutos a través de las raíces.
Hemos identificado y caracterizado un nuevo posible factor de transcripción dedo de zinc de tipo C2H2, homólogo a la proteína de Arabidopsis Sensitive to Proton Rhizotoxicity (STOP)1, la cual es crítica para la tolerancia a aluminio y protones en suelos ácidos. Hemos determinado que ZmSTOP1 es una proteína muy bien conservada entre especies, especialmente en sus cuatro dominios de tipo dedo de zinc, los cuales son característicos de las proteínas de tipo STOP1 en las plantas. ZmSTOP1 es miembro de una familia de cinco proteínas tipo STOP1 en maíz. Presenta localización nuclear y tiene la capacidad de unir ADN, aunque no se han podido identificar dianas específicas.
En este trabajo mostramos cómo ZmSTOP1 complementa el fenotipo característico de AtSTOP1 en condiciones de pH ácido. Además, detectamos que la sobreexpresión de ZmSTOP1 promueve una respuesta diferencial a ABA en raíces y hojas. El crecimiento de raíces está sobre inhibido, mientras que los estomas presentan insensibilidad a la señal de ABA, permaneciendo más abiertos que el control tras un tratamiento con ABA. Utilizando un análisis por microarray hemos podido determinar que los genes afectados por ZmSTOP1 se clasifican principalmente en señalización, regulación de la transcripción y estrés. Su sobreexpresión promueve cambios en el patrón de expresión de varios genes importantes para la homeostasis iónica y la señalización celular, como el canal de potasio KT2/3, el transportador de calcio CAX7, la NADPH oxidasa RBOHD, o la ATPasa de protones de membrana plasmática HA2, y puede inducir la expresión ectópica de estos genes en raíces u hojas. La desregulación de estos genes puede afectar el comportamiento global de la planta ante condiciones de estrés por sequía, ya que los efectos del ABA dependen profundamente en la homeostasis iónica, pudiendo representar una posible explicación para los fenotipos observados.
Adicionalmente, hemos establecido que esta proteína es interactor y sustrato de la quinasa OST1. La fosforilación por parte de esta quinasa modula el efecto de ZmSTOP1 en la regulación estomática.
En resumen, con la caracterización de la proteína ZmSTOP1 hemos arrojado luz sobre la compleja red que regula la tolerancia a estrés en una planta crucial para el consumo humano y animal como es el maíz. Estos resultados pueden ser importantes para enfocar futuras mejoras genéticas de la planta, ya sea por ingeniería genética o mediante mejora clásica.Water deficit has become a very important threat to agricultural yield worldwide. The identification of new players in drought stress response among crop plants is vital to understand their adaptation to increasing environmental challenges. Abscisic acid (ABA) is a plant hormone known to mediate drought adaptative responses such as seed dormancy, stomatal closure and root growth arrest. In the case of stomatal regulation, ABA drives the activation of OST1 kinase, which phosphorylates different substrates, for example NADPH oxidases, ionic channels and transcription factors, which will finally lead to stomatal closure. Although stomatal closure in response to ABA is essential to avoid desiccation, and thus, the death of the plant, a certain level of stomatal conductivity must be maintained to permit gas exchange and transpiration, essential to drive water and solutes uptake through the roots. We identified and characterized a new maize C2H2 zinc-finger putative transcription factor that presents homology to the Arabidopsis Sensitive to Proton Rhizotoxicity (STOP)1, which is critical for aluminum and proton tolerance in acidic soils. We determined that ZmSTOP1 is a well-conserved protein between plant species, especially in its four zinc-finger domains, which are characteristic of the STOP1-like proteins in plants. ZmSTOP1 is one of a five-members family of STOP1-like proteins in maize. It localizes in the nucleus, and has the ability to bind DNA, though no specific DNA targets were identified. In this work we show how ZmSTOP1 can complement AtSTOP1 phenotype in low pH conditions. Moreover, we detected that ZmSTOP1 overexpression promotes a differential response to ABA in roots and shoots. Root growth is over-inhibited whereas stomata present insensitivity to the ABA signal, remaining more open than the wild type after ABA treatment. Through microarray analyses we determine that the genes affected by ZmSTOP1 are classified mainly in signaling, regulation of transcription and stress. Its overexpression promotes changes in the expression pattern of several genes that are important for ionic homeostasis and signaling in cells, like the potassium channel KT2/3, the calcium transporter CAX7, the NADPH oxidase RBOHD, or the plasma membrane proton pump ATPase HA2, and it can induce ectopic expression of these genes in roots or shoots. The deregulation of these genes can affect the global behavior of the plant before drought stress conditions, as ABA effects depend deeply on ionic homeostasis, and could represent a possible explanation for the phenotypes observed. Additionally, we established that this protein is an interactor and a substrate of OST1 kinase. The phosphorylation by this kinase modulates ZmSTOP1 effect on stomatal regulation. In summary, by characterizing ZmSTOP1 protein we have shed light into the complex network regulating drought tolerance in a crucial plant for human and animal consumption like maize. These results can be important for focusing further genetic improvement of the plant, by either genetic engineering or classic breeding.
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Hjellström, Mattias. "Drought Stress Signal Transduction by the HD-Zip Transcription Factors ATHB6 and ATHB7." Doctoral thesis, Uppsala University, Physiological Botany, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1857.
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This work describes the regulation of drought stress responses in Arabidopsis thaliana and adresses the roles of the homeodomain-leucine zipper (HD-Zip) transcription factors in this regulation. The characteristics of ATHB6 and ATHB7, two genes encoding class I HD-Zip transcription factors were analysed.
Expression of ATHB6 and ATHB7 was transcriptionally activated in plants subjected to water deficit or exogenous treatment with abscisic acid (ABA).
Transgenic plants constitutively expressing the ATHB7 gene displayed a delayed elongation growth of the main inflorescence stem after transition to reproductive development. This phenotype is consistent with ATHB7 acting as a negative regulator of growth and development of the elongating stem in response to water availability.
Transgenic abi1-1 mutant plants constitutively expressing the ATHB7 gene displayed a reduced wiltiness as compared to monogenic abi1-1 mutants. These data are consistent with the ATHB7 protein having a central role in the drought stress response, regulating the water balance of the plant, and acting downstream to ABI1. Furthermore, the data is consistent with ATHB7 acting as a positive regulator of the drought stress response.
The ABA-induced expression of the ATHB7 gene displayed a dependence on the phytochrome system, suggesting an interplay between light and osmotic stress signaling in the regulation of the ATHB7 gene.
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Hjellström, Mattias. "Drought stress signal transduction by the HD-Zip transcription factors ATHB6 and ATHB7 /." Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2002. http://publications.uu.se/theses/91-554-5249-3/.
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James, Antonia Emily. "Investigating the effects of drought stress on emissions of biogenic volatile organic compounds." Thesis, Lancaster University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421622.
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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/.
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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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Tibbitts, Spencer A. "Effect of Silicon on Wheat Growth and Development in Drought and Salinity Stress." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/6925.
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Silicon is a major component of most soils, and is found in significant concentration in plant tissue. Plants vary widely in the amount of silicon they take up, with some plants excluding it, and others using transporters to move the silicon from the soil into their roots. Early plant physiology studies were unable to determine conclusively whether silicon was essential to plant growth, but for some plants, most notably rice, it has proved to be important enough to justify fertilizing silicon deficient fields.
Researchers at the USU Crop Physiology Lab tested the effect of silicon on wheat growth and seed yield components. One study was grown in buckets of peat moss, with half the buckets being stressed with low water. The other study was grown in hydroponic tubs, with half the tubs being stressed with high levels of salt.
The results from these studies showed that silicon does increase wheat seed yield and vegetative mass. Wheat with low levels of silicon exhibited twisting of the awns and decreased roughness of leaf surfaces. Silicon also improved water efficiency of drought stressed plants, and affected the concentration of many micro- and macro-nutrients in leaf tissue.
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Denny, Geoffrey Carlile. "Evaluation of selected provenances of taxodium distichum for drought, alkalinity and salinity tolerance." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1327.
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Duba, Nandipha. "Investigation of the link between drought-induced changes in the expression of a novel sterol biosynthesis gene and drought tolerance in soybean." University of the Western Cape, 2017. http://hdl.handle.net/11394/6338.
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Magister Scientiae - MSc (Biotechnology)Glycine max (soybean) is an important crop species globally as it is used as a protein-rich food and feed crop and as a source of oils used in the food and biofuel industry. However, the growth and yield of soybean is adversely affected by drought. Exposure of soybean to drought leads to accumulation of reactive oxygen species (ROS) and cell membrane instability. Sterols are membrane components that regulates membrane fluidity and permeability. Besides being major components of the cell membranes, sterols such as lanosterol appear to play a role in the regulation of ROS scavenging and some are precursors to brassinosteroids that act as signaling molecules with hormonal function that regulate growth, development and responses to abiotic stresses such as drought and salinity. In this study, the involvement of plant sterols, also known as phytosterols, in the regulation of soybean responses to drought stress was investigated in Glycine max by determining the effects of drought on the expression of a candidate lanosterol synthase gene (Glyma08g24160) and the content of a subset of phytosterols in soybean. The effects of inhibition of sterol synthesis on ROS production and on superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and dehydroascorbate reductase (DHAR) were investigated. The concentration of hydrogen peroxide (H2O2) as well as superoxide (O2-) increased in response to drought and sterol synthesis inhibition, however, O2- concentration and sterol contents declined under drought stress and sterol synthesis inhibition.
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Mutava, Raymond Ngao. "Evaluation of sorghum genotypes for variation in canopy temperature and drought tolerance." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/14506.
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Doctor of PhilosophyDepartment of Agronomy
P.V. Vara Prasad
Sorghum (Sorghum bicolor L. Moench) is the fifth most economically important cereal crop grown worldwide and adapted to a wide range of climatic conditions. Drought stress has been ranked as one of the most significant causes of crop yield loss with its effects on yield and yield components. Conservative water use by plants is one of the strategies that can be used as a drought coping mechanism. The slow wilting trait has been associated with conservative water use and has been found in some sorghum genotypes. The purpose of this study was to use canopy temperature to screen for drought tolerance in sorghum, evaluate water use efficiency for slow wilting sorghum genotypes and determine variability in root morphology and response to drought among sorghum genotypes. Canopy temperature studies were conducted under field conditions using infrared (IR) sensors while water use efficiency and root studies were conducted under greenhouse conditions. Our results showed a distinct separation in canopy temperature among genotypes under field conditions at 2:00 pm to 6:00 pm. Midday canopy temperature depression (CTD) was positively correlated to yield (R2 = 0.19) and harvest index (R2 = 0.11). CTD was also stable for all the genotypes during the period from 1:00 pm to 7:00 pm. There was a negative correlation between CTD and crop water stress index (CWSI) (R2 = 0.34) and a positive one between canopy temperature and CWSI (R2 = 0.50). Evaluation of genotypes for water use efficiency revealed significant variability among sorghum genotypes in the amount of water used (10.48 – 13.52 kg) and transpiration efficiency (TE) (2.64 – 7.11 g kg-1) among genotypes. Slow wilting genotypes were high in TE. Rooting depth increased for some genotypes under drought stress with genotype SC1124 recording the largest increase (180%). Total root length for some genotypes increased by 11 – 113% with genotypes SC224 and SC1019 recording the greatest increase. There was a positive correlation between water used and root length (R2 = 0.21). These results show that there is potential for selection of drought tolerance in sorghum and that genotypes with the slow wilting traits are efficient in water use.
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Toscano, Stefania. "Risposta di specie ornamentali allo stress idrico." Thesis, Università degli Studi di Catania, 2011. http://hdl.handle.net/10761/232.
Full textAbstract:
Nelle aree caratterizzate da clima mediterraneo lunghi periodi di carenza idrica durante la stagione primaverile-estiva, accompagnati da elevate temperature, possono determinare severi stress idrici in molte delle specie ornamentali impiegate per l'arredo urbano. Cio' in considerazione anche del fatto che non e' sempre possibile o conveniente, nella fase vivaistica e soprattutto di utilizzazione, un puntuale soddisfacimento delle loro esigenze per quanto concerne l'acqua. In tale contesto le prestazioni e la stessa sopravvivenza dipendono spesso dalla capacita' delle piante di assicurare un efficiente uso della risorsa idrica.
Nonostante l'interesse delle tematiche sottese, le questioni relative agli effetti dello stress idrico sulle specie ornamentali ed in particolare su quelle utilizzate per la sistemazione degli spazi a verde solo marginalmente sono state oggetto di studio. Solo recentemente i nuovi orientamenti in tema di progettazione e ricomposizione ambientale, sempre piu' rivolti a mettere a punto, schemi piu' sostenibili, hanno indirizzato le ricerche verso l'individuazione di interventi biologici e tecnici in grado meglio di valorizzare la risorsa idrica.
In questo contesto, contrassegnato da un livello di conoscenze assai limitato, l'obiettivo generale della presente tesi e' stato lo studio, in specie ornamentali diverse, degli effetti dello stress idrico ai semi, attraverso l'impiego di soluzioni osmotiche piu' o meno concentrate durante la fase di germinazione, o alle piante nelle prime fasi dell'accrescimento, mediante una piu' o meno drastica riduzione degli apporti idrici nel corso dellà ¢ intero ciclo colturale o di temporanee sospensioni degli interventi irrigui.
In particolare le prove sperimentali hanno riguardato:
A) Gli effetti dello stress idrico sulla germinazione e sullo sviluppo di plantule di girasole (Helianthus annuus L.).
B) La risposta morfo-fisiologica di arbusti ornamentali a condizioni differenziate di stress idrico.
C) I meccanismi morfo-fisiologici di recupero da stress idrico in arbusti ornamentali.
Nell'ambito di ciascuna prova gli obiettivi specifici sono stati:
A) Studiare, su sei cultivar di girasole ornamentale, gli effetti di differenti condizioni di stress idrico durante la fase di germinazione, sui principali parametri del processo in esame e sullà ¢ accrescimento delle plantule originate dai semi differentemente stressati.
B) Analizzare il comportamento di arbusti ornamentali diversi, sottoposti nei primi mesi del ciclo colturale a stress idrici di differente entita', al fine di valutare la loro tolleranza nei confronti della carenza di acqua nel substrato e di individuare i principali meccanismi morfo-biometrici e fisiologici che sostengono la tolleranza stessa.
C) Valutare, in cinque arbusti ornamentali largamente utilizzati per la ricomposizione di spazi a verde, la capacita' di recupero allo stress idrico a seguito di periodici interventi di sospensione e ripristino degli interventi irrigui.
Le prove rivolte a valutare gli effetti dello stress idrico, imposto attraverso l'adozione di livelli di potenziale osmotico differenti, sul processo di germinazione di cv di girasole, hanno consentito di acquisire risultati circa: a) il valore limite del potenziale osmotico della soluzione al di sotto del quale il processo non si realizza; b) il comportamento, apparso piuttosto diverso tra loro, delle cultivar allo studio nei confronti dello stress idrico nel corso della germinazione stessa; c) la possibilita', attraverso la adozione di soluzioni con potenziale osmotico lievemente negativo, di migliorare la germinazione in termini sia quantitativi che temporali. La scarsa concordanza riscontrata, in rapporto alle cv, tra il loro comportamento nei confronti dello stress idrico in fase di germinazione e l'accrescimento delle relative plantule, sollecita ulteriori verifiche, considerato il notevole interesse che riveste la possibilita' di effettuare uno screening precoce, semplice e assai rapido, per la selezione dei genotipi per il carattere in oggetto.
Le prove concernenti gli effetti esercitati in arbusti ornamentali diversi dallo stress idrico nelle prime fasi dell'accrescimento, e che hanno preso in esame le modificazioni causate sulla pianta sia dalla differente disponibilita' di acqua nel substrato nel corso dell'intero ciclo colturale che da periodici interventi di sospensione e ripristino degli interventi irrigui hanno messo in luce profonde differenze fra specie in esame. Queste ultime, infatti, sebbene siano apparse tutte idonee ad essere impiegate in quegli ambienti in cui le risorse idriche sono assai limitate, hanno mostrato una differente capacita' di valorizzare condizioni di scarsa disponibilita' di acqua. La tolleranza agli stress idrici, in particolare, e' apparsa legata fortemente a modificazioni morfo-biometriche e fisiologiche della pianta, che hanno interessato nel primo caso l'apparato fotosintetizzante e quello radicale, nel secondo la conduttanza stomatica. In genere, in condizioni di scarsa disponibilita' di acqua nel substrato, le specie meno tolleranti hanno messo in atto meccanismi di difesa basati essenzialmente sulla diminuzione delle dimensioni dell'apparato fotosintetizzante, mentre le specie apparse piu' tolleranti agli stress idrici si sono principalmente affidate all'aumento delle dimensioni degli apparati radicali. Per quanto concerne i meccanismi fisiologici, la modificazione della conduttanza stomatica e' apparsa la strategia principalmente impiegata per contenere le perdite di acqua.
In ogni caso, un elemento che emerge dalle prove, e che certamente contribuisce alla notevole tolleranza agli stress idrici da parte delle specie studiate, e' la loro capacita', sia pure in misura diversa, di recuperare, al termine del periodo sfavorevole, la piena efficienza funzionale, come si evince dall'andamento di molti dei processi fisiologici monitorati.In the areas characterized by Mediterranean climate, long periods of water deficit during the spring-summer season together with high temperatures, could determine severe water stress in many ornamental species utilized for urban landscape. Moreover, it is not always possible or convenient to satisfy plant water requirements, both in the nursery and in the following growth stages. Therefore, the growth and survival of these species is linked to their capacity to increase the water use efficiency. Nevertheless the importance of these issues, little investigation has been done on water stress of ornamental shrubs, and especially in the ones utilized for landscape. However the new trends on â sustainable landscapingâ have paid the attention on the individuation of biological and technical tools for a better valorization of water resources. In this frame, the general aim of the PhD thesis was to study, on several ornamental species, the effect of water stress determined by solutions with different osmotic potential during germination and by different restitution of water loss with evapotranspiration during growth cycle. The experimental trials concerned: A) The effects on water stress on germination and seedling growth in sunflower (Helianthus annuus L.). B) Morpho-physiological response of ornamental shrubs in different water stress conditions. C) Morpho-physiological mechanisms of water stress recovery in ornamental shrubs. The specific aim for each trial was: A) Study on six sunflower cultivars the effects of different water stress conditions on germination rate and seedling growth rate; B) Analyze the behavior of several ornamental shrubs subjected in the first period of growth cycle to water stress to individuate the tolerance on water deficit in the substrate. Moreover the main mechanisms morpho-biometrical and physiological have been investigated. C) Evaluate on five ornamental shrubs largely used in the landscape, the recovery capacity to water stress after periodical cycles of suspension/recovery of irrigation. In the trial on the evaluation of water stress imposed with different osmotic potentials on sunflower germination, different results were obtained: a) the osmotic potential threshold (below this value germination does not start); b) different behavior of the studied cultivars in relation to water stress and germination; c) the possibility to enhance the germination trough the adoption of solutions with low osmotic potentials. The different results in relation to the cultivars in the two steps (seed and seedling growth stages) need further investigation considering the noticeable interest to effectuate a quick and easy screening for evaluation of genotypes to water stress. The response of ornamental shrub seedlings to water stress has considered the plant changes to different water content in the substrate for the whole cultivation period and to frequent cycles of suspension/recovery of irrigation. Results showed that species seemed to be available in environments characterized by scarce water resources, and exhibited a different capacity to increase water efficiency. The tolerance to water stress is linked to morpho-biometrical and physiological changes, which have involved the photosynthesis and stomatal conductivity. In low water availability less tolerant species showed a reduction in leaf area, while the tolerant ones have increased the root systems. Among the physiological mechanisms, the modification of stomatal conductivity appears to be the main strategy to avoid water loss. However, as showed by the many physiological processes investigated, species showed a certain capability (different among the species) to recover their functional efficiency at the end of unfavorable period.
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Pfunde, Cleopatra Nyaradzo. "Parent characterization of quality protein maize (Zea mays L.) and combining ability for tolerance to drought stress." Thesis, University of Fort Hare, 2012. http://hdl.handle.net/10353/d1007536.
Full textAbstract:
Quality protein maize (QPM) has enhanced levels of two essential amino acids, lysine and tryptophan compared to normal maize. This makes QPM an important cereal crop in communities where maize is a staple crop. The main abiotic factor to QPM production is drought stress. Little information is available on the effect of drought stress on QPM. Therefore, the objectives of this study were to: (i) conduct diversity analysis of QPM inbred lines using morpho-agronomic and simple sequence repeat markers, (ii) screen available QPM inbred lines and F1 progeny for tolerance to seedling drought stress, (iii) determine the combining ability and type of gene action of QPM inbred lines for tolerance to seedling drought stress, grain yield and endosperm modification. The study was conducted in South Africa, at the University of Fort Hare. Morphological characterisation of 21 inbred lines was done using quantitative and qualitative traits. A randomised complete block design with three replicates was used for characterizing the inbred lines in the field. Genstat statistical software, version 12 (Genstat ®, 2009) was used for analysis of variance (ANOVA) and descriptive statistics. Analysis of variance was performed on all quantitative data for morphological traits. Data for qualitative traits was tabulated in their nominal classes. Traits that contributed most to the variation were days to anthesis, days to silking, anthesis-silking interval, plant height, number of kernel rows, ear length and grain yield. Cluster analysis grouped the inbred lines into three main clusters. The first cluster was characterised by tall and average yielding lines, while the second cluster showed the least anthesis-silking interval, and had the highest yield. Cluster three consisted of lines that were early maturing, but were the least yielding. Genetic distances between maize inbred lines were quantified by using 27 simple sequence repeat markers. The genetic distances between genotypes was computed using Roger’s (1972) genetic distances. Cluster analysis was then carried out using the neighbour-joining tree method using Power Marker software version 3.25. A dendrogram generated from the genetic study of the inbred lines revealed three groups that concurred with expectations based upon pedigree data. These groups were not identical to the groups generated using morpho-agronomic characterisation. Twenty one QPM inbred lines were crossed using a North Carolina design II mating scheme. These were divided into seven sets, each with three inbred lines. The three inbred lines in one set were used as females and crossed with three inbred lines in another set consisting of males. Each inbred line was used as a female in one set, and as a male in a second set. Sixty three hybrids (7 sets x 9 hybrids) were formed and evaluated in October 2011, using a 6x8 alpha-lattice incomplete block design with three replicates under glasshouse and optimum field conditions. A randomised complete block design with three replicates was used for the 21 parental inbred lines. Traits recorded for the glasshouse study were, canopy temperature, chlorophyll content, leaf roll, stem diameter, plant height, leaf number, leaf area, fresh and dry root and shoot weights. Data for the various traits for each environment, 25 percent (stress treatment) and 75 percent (non-stress) of field capacity, were subjected to analysis of variance using the unbalanced treatment design in Genstat statistical package Edition 12. Where varietal differences were found, means were separated using Tukey’s test. Genetic analyses for grain yield and agronomic traits were performed using a fixed effects model in JMP 10 following Residual Maximum Likelihood procedure (REML). From the results, inbred lines that were not previously classified into heterotic groups and drought tolerance categories were classified based on their total dry weight performance and drought susceptibility index. Inbred lines L18, L9, L8, L6 and L3, in order of their drought tolerance index were the best performers under greenhouse conditions and could be recommended for breeding new varieties that are tolerant to seedling drought stress. Evaluation of maize seedlings tolerant to drought stress under glasshouse conditions revealed that cross combination L18 x L11 was drought tolerant, while cross L20 x L7 was susceptible. Total dry weight was used as the major criteria for classifying F1 maize seedlings as being resistant or susceptible. General combining ability effects accounted for 67.43 percent of the genetic variation for total dry weight, while specific combining ability effects contributed 37.57 percent. This indicated that additive gene effects were more important than non-additive gene action in controlling this trait. In the field study (non-drought), the experimental design was a 6x8 alpha lattice incomplete block design with three replicates. On an adjacent field a randomised complete block design with three replicates was used to evaluate the parental inbred lines. The following variables were recorded: plant height, ear height, ears per plant, endosperm modification, days to silking and days to anthesis, anthesis-silking interval, number of kernels per row, number of rows per ear and grain yield. General analyses for the incomplete lattice block design and randomised complete block design for hybrid and inbred data respectively were performed using JMP 10 statistical software. Means were separated using the Tukey's test. Genetic analyses of data for grain yield and agronomic traits were conducted using a fixed effects model using REML in JMP 10. The importance of both GCA (51 percent) and SCA (49 percent) was observed for grain yield. A preponderance of GCA existed for ear height, days to anthesis, anthesis-silking interval, ears per plant and number of kernels per row, indicating that predominantly, additive gene effects controlled hybrid performance under optimum field conditions. The highest heritability was observed for days to silking (48.27 percent) suggesting that yield could be improved through selection for this trait. Under field conditions, variation in time to maturity was observed. This implies that these inbred lines can be recommended for utilisation in different agro-ecologies. Early maturing lines such as L18 can be used to introduce earliness in local cultivars, while early maturing single crosses such as L18 x L2, L5 x L9, L3 x L4 and L2 x L21 could be recommended for maize growers in drought prone areas such as the former Ciskei. Single crosses L18xL11, L16xL18, L8xL21 and L9xL6 had good tolerance to seedling drought stress. On the other hand, single crosses L18xL11 and L11xL13 had high grain yield and good endosperm modification. All these single crosses could be recommended for commercial production after evaluation across locations in the Eastern Cape Province. Alternatively they can be crossed with other superior inbreds to generate three or four way hybrids, which could then be evaluated for potential use by farmers in the Eastern Cape.