Tesi sul tema "Water stress"
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1
Umponstira, Chanin. "Ozone and water stress interactions". Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341462.
Testo completo
2
Al-Najafi, Mohammad Abdul Aziz. "Root shrinkage in relation to water stress". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279828.
Testo completo
3
Perez, Jose 1950. "WATER AND NITROGEN EFFECTS ON THE CROP WATER STRESS INDEX OF COTTON". Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275339.
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Spinelli, Gerardo. "Water Stress And Water Use Of Almonds In California| Linking Plant Water Status And Canopy Transpiration". Thesis, University of California, Davis, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3723733.
Testo completoAbstract (sommario):
Almond water use was investigated at the leaf, plant and canopy level under a range of irrigation conditions in commercial orchards in California. Understanding plant response to water stress, specifically the behavior of plant transpiration and water use during periods of water stress, has important implications for irrigation scheduling in agriculture but also for water resources management and policy making.
Leaf gas exchange measurements of stomatal conductance and photosynthetic rate were performed at midday on shaded and on sunlit leaves, with midday stem water potential used to assess plant water stress. An essentially linear decline in both photosynthetic rate (from 25 to 5 μmol m-2 s-1) and stomatal conductance (from 400 to 50 mmol m -2 s-1) as stem water potential declined over the range of -0.5 to -3 MPa was observed in sunlit leaves. These data indicated a strong sensitivity of leaf-level physiological processes to water stress. However, evapotranspiration at the canopy level, measured using Eddy Covariance, did not show a reduction relative to atmospheric demand during periods of water stress. The apparent disconnect observed between leaf conductance, responsive to water stress and canopy evapotranspiration, insensitive to water stress, is the central problem investigated in this study.
When the transpiration data was analyzed in the framework of a "Big Leaf" model, decoupled conditions (i.e. a limited stomatal control of transpiration) were shown to prevail at the experimental site, contrary to previous findings reported in the literature for tall crops such as almond orchards. Low coupling implies only a moderate sensitivity of transpiration to stomatal closure. Measured coupling increased substantially with wind speed but showed a wide range of values at the low wind speeds (<1m s-1) that were observed at the site. At any wind speed however, higher canopy resistance resulted in higher coupling. The high leaf area index observed in the orchard may have been responsible for causing decoupled conditions, because when leaf area decreased as a result of harvesting operations, canopy transpiration appeared to become more sensitive to water stress.
Cumulative daily sap velocity was used as an estimate of plant transpiration. At the plant level, contrasting behaviors were observed in plant transpiration in the presence of water stress, depending on the duration and intensity of the stress. During long soil dry-down periods encompassing several weeks, plant transpiration relative to the evaporative demand of the atmosphere showed a statistically significant decline associated with a decrease in stem water potential and in stomatal closure. However, when the cycle of water stress was short (days), reductions in stem water potential seemed to be associated with an increase in cumulative sapflow velocity. The analysis of these results led to the development of a simple model that describes the theoretical interactions between three dependent variables, namely stem water potential, stomatal conductance and transpiration. The model output suggested that in wet soil, an increase in transpiration may be caused by increasing evaporative demand even if stem water potential and stomatal conductance decrease.
5
Lehle, F. R., e A. M. Zegeer. "Effects of Oxygen Stress and Water Stress on Cotton (Gossypium hirsutum) Seed Growth". College of Agriculture, University of Arizona (Tucson, AZ), 1989. http://hdl.handle.net/10150/204832.
Testo completoAbstract (sommario):
The effects of oxygen stress and water stress on cotton seed radicle growth was studied. High vigor Deltapine 90 seed were imbibed in individual test tubes at 28°C for 28 hours. Seed were then subjected for 2 hours at 28°C to either 1) oxygen stress imposed by N₂ gas, 2) water stress imposed by polyethylene glycol 6000 (0.8 gm mL water⁻¹), or 3) a combination of both 1) and 2). Following imposition of either oxygen stress or water stress, radicle growth stopped temporarily; growth resumed while either stress was still imposed but at a greatly reduced rate relative to the unstressed control. Cotton radicle growth was prevented however, in the presence of both oxygen and water stress. The prevention of growth was reversible, as growth resumed when both stresses were relieved.
6
French, Robert John. "Leaf senescence and water stress in wheat seedlings /". Title page, contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09PH/09phf875.pdf.
Testo completo
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Otto, Marina Shinkai Gentil. "Physiological responses of forest species to water stress". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/11/11144/tde-05112015-154241/.
Testo completoAbstract (sommario):
Abiotic and biotic stresses affect tree growth and play a major role in determining the geographic distribution of species. The objective of this study is to elucidate the following questions: (1) are GABA aminoacid and stomatal control good indicators of tolerance to water stress in Eucalyptus clones? In addition, what are the anatomical differences between drought-tolerant and drought-sensitive clones of Eucalyptus? (2) Are there differences of xylem vulnerability to cavitation in Pinus flexilis families susceptible and resistant to white pine blister rust (WPBR) and with different origins (high and low altitudes)? Two studies were carried out to elucidate the issues above. On chapters 1, eight Eucalyptus clones from different geographical and climatological conditions, three drought-sensitive (CNB, FIB and JAR), three drought-tolerant (GG, SUZ and VM), and two plastics (VER and COP), were studied in normal water supply (control treatment) and in water stress conditions (stress treatment). The first chapter concluded that GABA is an aminoacid very sensitive to water stress, but there was no relation between GABA concentration and tolerance to water stress of the clones. In addition, all clones decreased stomatal conductance with increasing vapor pressure deficit, and plastics and drought-tolerant clones (except GG) presented lower stomatal sensitivity to vapor pressure deficit under stress conditions than drought-sensitive clones. Besides, all clones showed differences on the anatomical parameters between, and only COP (plastic) and SUZ (drought-tolerant) showed homogeneous mesophyll and amphi-hipostomatic leaves. All clones increased the number of stomata and reduced leaf thickness of the leaves formed after water stress period. On the chapter 2, we studied 12 families of Pinus flexilis originating from high and lower altitudes, in which six families previously shown to contain the dominant C4 allele (resistant to WPBR) and six families without C4 allele (susceptible to WPBR). This study showed that the mean cavitation pressure (MCP) of Pinus flexilis varying between 3.63 a -4.84 Mpa, although there was a significant difference in vulnerability to cavitation comparing all families, this variable was not related to WPBR and origin region. These studies highlight that the physiological responses of plants under water stress conditions are important tools that can be used to complement the strategies of genotype selection in forest breeding programs.Estresses abióticos e bióticos podem afetar o crescimento das árvores e desempenham um papel importante na determinação da distribuição geográfica das espécies. O objetivo deste estudo, foi elucidar as seguintes questões: (1) o aminoácido GABA e o controle estomático são bons indicadores da tolerância ao estresse hídrico em clones de Eucalyptus? E quais são as diferenças anatômicas entre clones de Eucalyptus tolerantes e sensíveis ao estresse hídrico? (2) existem diferenças de vulnerabilidade a cavitação do xilema entre famílias de Pinus flexilis suscetíveis e resistentes à ferrugem do pinho branco (WPBR) e com diferentes procedências (elevada e baixa altitudes)? Dois estudos foram desenvolvidos para elucidar as questões acima descritas. No capítulo 1, oito clones de Eucalyptus de diferentes procedências e condições climáticas, sendo três clones sensíveis ao estresse hídrico (CNB, FIB e JAR), três clones tolerantes ao estresse hídrico (GG, SUZ e VM) e dois clones plásticos (VER e COP), foram estudados sob duas condições distintas: sob adequado suprimento de água (tratamento controle) e sob condições de estresse hídrico (tratamento estresse). Do primeiro capítulo concluiu-se que o GABA é um aminoácido que possui alta sensibilidade ao estresse hídrico, no entanto, não houve relação entre a concentração de GABA e os níveis de tolerância ao estresse hídrico dos clones. Além disso, todos os clones reduziram a condutância estomática em relação ao aumento do déficit de pressão de vapor (DPV), sendo que, sob condições de estresse hídrico, os clones plásticos e tolerantes à seca (exceto o clone GG) apresentaram menor sensibilidade estomática ao DPV do que os clones sensíveis ao estresse hídrico. Além disso, todos os clones apresentaram diferenças anatômicas, sendo que, diferentemente dos demais, os clones COP (plástico) e SUZ (tolerante) apresentaram mesofilo homogêneo e folhas anfi-hipoestomáticas. Todos os clones aumentaram a quantidade de estômatos e reduziram a espessura foliar das folhas formadas após períodos de estresse hídrico. No segundo capítulo foram avaliadas 12 famílias de Pinus flexilis procedentes de regiões de baixa e alta altitudes, sendo seis famílias contendo um alelo dominante C4 (resistente à WPBR) e seis famílias sem o alelo C4 (suscetíveis à WPBR). Este estudo apresentou uma variação da pressão média da cavitação (MCP) para Pinus flexilis de -3,63 a -4,84 Mpa, e embora tenha havido uma diferença significativa da susceptibilidade a cavitação entre todas as famílias estudadas, esta variável não relacionou-se com a susceptibilidade a doença WPBR e com a região de procedência das famílias. Estes estudos comprovam que a avaliação das respostas fisiológicas das plantas sob condições de estresse hídrico são importantes ferramentas que podem ser utilizadas para complementar as estratégias da seleção de genótipos em programas de melhoramento florestal.
8
Beckett, Heath. "Remote sensing of water stress in fynbos vegetation". Bachelor's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/25902.
Testo completoAbstract (sommario):
I aim to determine whether or not remote sensing, through multispectral, satellite and digital photography, is a feasible and accurate method for determining drought stress in Fynbos vegetation. I hypothesize that (1) water stress in fynbos is detectable with the use of a remote sensing index, namely NDVI and (2) that the remotely sensed trends will correlate with ground truth measures of water stress.
9
Correia, Barbara dos Santos. "Water stress and recovery in Eucalyptus: physiological profiles". Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/10165.
Testo completoAbstract (sommario):
Mestrado em Biologia AplicadaEm Portugal, cerca de 700,000 ha foram já plantados com clones de Eucalyptus globulus, selecionados pelas suas elevadas taxas de crescimento, alta produção de polpa e adaptabilidade ambiental. Contudo, a produtividade das plantações de E. globulus tem enfrentado sérias limitações, principalmente devido à fraca disponibilidade de água. A seca é um importante stress abiótico que afeta negativamente o crescimento e o desenvolvimento das plantas, causando um conjunto de respostas fisiológicas, bioquímicas e moleculares. Embora esteja disponível um grande número de estudos que descreve as respostas das plantas ao stress hídrico, apenas alguns trabalhos se debruçam sobre os mecanismos que permitem a recuperação. Além disso, vários estudos descrevem também como diferentes genótipos podem diferir na capacidade de lidar com a seca. Considerando que manter a produção durante o stress hídrico não é o mais relevante, mas sim a capacidade de sobreviver e recuperar rapidamente após a re-hidratação, o objetivo deste estudo foi compreender os mecanismos envolvidos na recuperação, de modo a selecionar coleções clonais adequadas a plantações sustentáveis num clima mediterrânico. Com essa finalidade, dois clones de E. globulus (AL-18 e AL-126) foram submetidos a um período de três semanas em stress hídrico, seguido por uma semana de recuperação. Um perfil fisiológico foi obtido para cada genótipo, pela avaliação do crescimento, estado hídrico, peroxidação lipídica, respostas do aparelho fotossintético, trocas gasosas e concentração de ABA. Os principais resultados deste trabalho levam a concluir que: i) os genótipos escolhidos foram altamente tolerantes às condições testadas; ii) os clones selecionados apresentaram uma resposta similar na maioria dos parâmetros testados (exceto MDA, pigmentos, parâmetros fotossintéticos e ABA); iii) o clone AL-126 foi o mais resiliente à seca, mantendo taxas de crescimento mais elevadas em stress e após re-hidratação.
In Portugal, about 700,000 ha have been established with Eucalyptus globulus clones selected for their high growth rates, high pulp yield and environmental adaptability. However, productivity in E. globulus plantations has encountered serious limitations, mostly because of water availability. Drought is a major abiotic stress negatively affecting plant growth and development that causes an array of physiological, biochemical and molecular responses in plants. Apart from the great number of studies reporting on plant responses to drought stress and on the mechanisms to overcome stressful conditions, only a few reports providing evidence about the capacity of recovery and the underlying processes during recovery from drought are available. Moreover, ecophysiological studies have reported that different genotypes differ in their capacity to cope with drought. Considering that maintenance of production during drought is not the most important consideration, but rather the capacity to survive and recover rapidly after rewatering, the aim of this study was to understand the underlying mechanisms in recovery in order to select suitable clonal collections for sustainable plantations in a Mediterranean climate. For this propose, two E. globulus clones (AL-18 and AL-126) were subjected to a three-week water stress period, followed by one week recovery. A physiological profile was obtained for each genotype, assessing growth, water status, lipid peroxidation, photosynthetic responses, gas exchanges and ABA concentration. The main results of this work led us to conclude that: i) the chosen genotypes were highly tolerant to the conditions tested; ii) the selected clones presented a similar response in most of the tested parameters (except for MDA, pigments, fluorescence parameters and ABA); iii) clone AL-126 was the most resilient to drought, maintaining higher growth rates under stress and after rewatering.
10
Berenguer, Helder Duarte Paixão. "Eucalyptus predisposition to Neofusicoccum kwambonambiense under water stress". Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/22330.
Testo completoAbstract (sommario):
Mestrado em Biologia Molecular e CelularIn Portugal, Eucalyptus, particularly Eucalyptus globulus, occupies more than 800 000 ha and, due to being a major source of biomass for fiberboard, industrial charcoal, fuel wood and paper pulp, has become a key genus, with a considerable economic importance. However, E. globulus productivity faces new pressures, with climate change-driven drought as one of the most hostile ones. Drought can lead to growth impairment and yield reduction: directly; or indirectly, through the increase of plant susceptibility to pathogens by a predisposition mechanism. Neofusicoccum kwambonambiense is an endophytic opportunist phytopathogen known to severely affect E. globulus, whose incidence has already been reported in Portugal. Taking all in consideration, it is of major importance to assess the predisposition effect that drought may have on the N. kwambonambiense - E. globulus interaction. For such purpose, four treatment groups were established: E. globulus were firstly subjected to a 66-days acclimation period in which plants were periodically watered (80% of field capacity). After that, two groups were exposed to a progressive water supply restriction. The other two remained well-watered. Once water-stressed plants achieved 18% of field capacity (23 days), a well-watered and a water-stress group were inoculated with N. kwambonambiense. All treatments were kept in these conditions throughout a 65 days’ period, at which moment a set of morphological, physiological and biochemical parameters was obtained. Well-watered plants, despite being infected with N. kwambonambiense, presented an overall photosynthetic increase, which enabled plant defense through the production of sugars, proline and salicylic acid. Oxidative damages (partially observed through malondialdehyde content), were avoided in part due to proline and soluble sugars. Water stress lead to a direct growth impairment confirmed through an indole-acetic-acid content decrease. A water-potential reduction occurred, which, together with abscisic acid, lead to stomatal closure and overall photosynthetic efficiency decline. Oxidative damages weren’t properly managed and further affected E. globulus. Furthermore, N. kwambonambiense was found to promote a jasmonic acid content increase, typical of necrotrophic pathogens, which may suggest a lifestyle change from hemibiotrophic to necrotrophic as plant cells progressively degenerate. Ultimately, water-stressed E. globulus presented larger external lesion extensions and steam cankers and a superior internal fungi progression. Our results conclusively demonstrate that water stress created a better substrate for fungi development and decreased the plant’s ability to respond. Such resulted in higher susceptibility and disease severity confirming predisposition.
Em Portugal, o eucalipto, particularmente o Eucalyptus globulus, ocupa mais de 800 000 ha. Devido a ser uma importante fonte de biomassa para painéis de fibras, carvão industrial, lenha e pasta de papel, tornou-se um género chave de considerável importância económica. Contudo, a produtividade de E. globulus tem encontrado novas pressões, sendo a seca resultante das alterações climáticas, uma das mais hostis. A seca pode levar a uma diminuição do crescimento e produtividade: diretamente; ou indiretamente através do aumento da suscetibilidade a agentes patogénicos através da predisposição. O fungo ascomiceto Neofusicoccum kwambonambiense é um agente fitopatogénico endofítico oportunista que se sabe afetar severamente E. globulus, e cuja presença já fora confirmada em Portugal. Tomando tal em consideração, torna-se importante avaliar o efeito de predisposição que a seca poderá ter na interação N. kwambonambiense - E. globulus. Para tal foram criados quatro grupos de tratamento: E. globulus foram primeiramente sujeitos a um período de aclimatização de 66 dias no qual foram periodicamente irrigados (80% de capacidade de campo). Seguidamente, dois grupos foram sujeitos a uma diminuição progressiva da irrigação. Os outros dois grupos permaneceram bem regados. Uma vez que os tratamentos stressados atingiram 18% de capacidade de campo (23 dias), um grupo bem regado e um grupo stressado foram inoculados com N. kwambonambiense. Todas os tratamentos foram mantidos nestas condições durante um período de 66 dias, findo o qual foi obtido um conjunto de parâmetros morfológicos, fisiológicos e bioquímicos. As plantas bem regadas, apesar de terem sido inoculadas com N. kwambonambiense apresentaram um aumento dos parâmetros fotossintéticos o que terá permitido a defesa da planta através de uma produção amplificada de açúcares, prolina e ácido salicílico. Danos oxidativos (parcialmente observados através do conteúdo em malondialdeído) foram evitados, em parte, devido à ação da prolina e açúcares solúveis. O stress hídrico levou a uma diminuição do crescimento confirmado pela redução do conteúdo em ácido-indole-acético. Ocorreu uma diminuição do potencial hídrico, a qual, em conjunto com o aumento do ácido abscísico, levou ao fecho dos estomas e diminuição da fotossíntese. Os danos oxidativos não foram controlados, afetando o estado do E. globulus. Ademais, o N. kwambonambiense provocou um aumento do conteúdo em ácido jasmónico, típico de agentes patogénicos necrotróficos, o que poderá sugerir que o fungo passou de um estilo de vida hemibiotrófico para necrotrófico, à medida que as células degeneravam. Os E. globulus stressados apresentavam maiores lesões externas e cancros, conjuntamente com uma maior progressão interna do fungo. Os nossos resultados comprovam que a seca criou um melhor substrato para o desenvolvimento do fungo e diminuiu a capacidade de resposta da planta. Tal resultou num aumento da suscetibilidade e severidade da doença confirmando a predisposição.
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Husman, S., F. Metzler, R. Wegener, K. Johnson, L. Schnakenberg, P. Brown e E. Martin. "Upland Cotton Water Stress Sensitivity By Maturity Class". College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/210897.
Testo completoAbstract (sommario):
Lint yield response to three irrigation treatments based on allowable soil moisture depletion regimes of 50, 75, and 100% depletion of available soil moisture was tested on both a determinate (D&PL 5415) and an indeterminate (D&PL 5816) upland cotton. Arizona Meteorological Weather Networks' (AZMET) potential evapotranspiration (ETo) estimates in combination with cotton crop coefficients were used in a summation manner until targeted depletion thresholds were reached which then triggered the desired irrigation event. The experiment consisted of three irrigation treatments with each main irrigation treatment containing both the determinate and indeterminate variety selection resulting in a randomized complete block split plot design. Actual irrigation volume delivered was 46, 42, and 32 acre inches /acre in 1994 and 52, 48, and 36 acre inches /acre in 1995 for the wet, medium, and dry treatment respectively. Lint yields were significantly reduced in 1994 when available soil moisture depletion exceeded 75% in the determinate variety with no significant yield differences in the indeterminate variety in 1994 across all irrigation treatment regimes. In 1995, lint yields were down across all treatments and varieties with the only statistically significant reduction in lint yield (relative to all 1995 yields) occurring in the dry indeterminate block
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Garrot, D. J. Jr, M. W. Kilby, D. D. Fangmeier e S. H. Husman. "Quantification of Pecan Water Stress for Irrigation Scheduling". College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/215744.
Testo completo
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CARAMANICO, LEILA. "STUDY OF GRAPEVINE ROOTSTOCK RESPONSE TO WATER STRESS". Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/707586.
Testo completoAbstract (sommario):
More than 80% of vineyards around the world use grafted plants: a scion of Vitis vinifera grafted onto a rootstock of single or interspecific hybrids of American Vitis species, resistant or partially resistant to Phylloxera (Daktulosphaira vitifoliae (Fitch, 1856)). The genetic variability of grapevine rootstocks plays a fundamental role in their adaptation to the environment (Serra et al., 2013). In the climate change scenario, predicting an increase of aridity in the near future (Dai, 2013), the more frequent and severe drought events may represent the major constrain for the future of viticulture (IPCC, 2018; Schultz, 2000). Therefore, the selection of new rootstocks able to cope with unfavourable environmental condition is a key asset, as well as a strategy to improve crop yield/vegetative growth balance on scion behaviour (Corso and Bonghi, 2014).
So far, the influence of rootstock on scion physiological performance during water stress has always aroused great interest. On the contrary, the scion impact on rootstock response is still less debated. Therefore, the effect of grafting on rootstock behaviour have been investigated. Phenotypical and large-scale whole transcriptome analyses on two genotypes, a drought-susceptible (101-14) and a drought-tolerant (1103 P), own-rooted and grafted with Cabernet Sauvignon, subjected to a gradual water shortage in semi-controlled environmental conditions have been performed. The ungrafted condition affected photosynthesis and transpiration, meaning the decisive role of scion in modulation of gas exchanges and in general in plant adaptation. Molecular evidence highlighted that the scion delays the stimulus perception and rootstock reactivity to drought.
Since 1985, the DiSAA research group operating at the University of Milan is carrying on a rootstock crossbreeding program which has led to the release of four genotypes: M1, M2, M3 and M4. They show from moderate to high tolerance to drought (M4 > M1 = M3 > M2). In order to characterize their performance during water stress, their physiological (gas exchanges and stem water potential) and transcriptome response (genes involved in ABA-synthesis and ABA-mediated responses to drought) under well-watered and water stress conditions were examined. The behaviour of M-rootstocks (M1, M2 and M3) was compared with that of other commercial genotypes largely used in viticulture, either tolerant (140 Ru, 41 B, 110 R, 1103 P), less tolerant (SO 4, K 5BB) and susceptible (420 A and Schwarzman). Discriminant analysis (DA) showed that when water availability starts to decrease, rootstocks firstly perceives the stress activating a transcriptome response, consequently physiological changes have been observed. It also demonstrated that the three M-rootstocks were clearly discriminated: M4 was grouped with the most tolerant genotypes while M3 with the less tolerant or susceptible ones from a physiological standpoint, confirming their different attitude to tolerate water stress.
M4 has proven to be a promising rootstock due to its ability to adapt to drought conditions. Considering the constant great demand for vine planting materials, the obtainment of genetically homogeneous populations (i.e. clones) from elite individuals through micropropagation represents a rapid alternative to conventional multiplication. For this reason, an efficient high-throughput protocol for M4 in vitro propagation was set up. Its attitude to shooting, root development and callus proliferation was compared to that of other rootstocks largely used in viticulture (K5BB, 1103P, 101-14 and 3309C). Moreover, pro-embryogenic and embryogenic callus from bud explants were also produced, representing a cellular material manipulable with the genetic engineering techniques.
In water scarcity condition, among the mechanisms activated by M4, the great ability to scavenge ROS, related to the increased accumulation of stilbenes and flavonoids, may be such as to give it tolerance to the stress. In particular, the higher levels of trans-resveratrol were correlated with the up-regulation of some stilbene synthase genes, mainly VvSTS16, VvSTS18, VvSTS27 and VvSTS29. The over expression of these genes was linked to a structural variation in their promoter region. To confirm that VvSTSs genes may be considered putative factors of M4 better adaptation to water stress, a genome editing protocol based on the CRISPR/Cas9 system, aimed at knock-out the genes, was performed. For testing the gRNAs functionality, a transient assay on in vitro micropropagated plantlets of M4 and 101-14 was performed. The positive results obtained by this experiment will lead to the transformation of somatic embryos and regeneration of whole-edited plants using the vectors developed.
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Zhang, Li. "Grapevine root growth under water stress and its relationship to root water uptake". Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0893.
Testo completoAbstract (sommario):
Le sujet de l’adaptation aux changements climatiques est devenu l’un des sujets contemporains les plus importants dans la vigne. Une grande focalisation a été mise sur la compréhension des effets du porte-greffe sur la croissance du scion, l’absorption des nutriments, et la tolérance au stress, dans l’objectif final de développer de nouveaux porte-greffes qui facilitent l’adaptation au changement climatique. L’objectif de cette thèse est d’examiner comment les différences dans la résistance à la sécheresse entre les génotypes peut résulter en de grandes différences dans leur capacité à maintenir leur croissance racinaire en situation de stress. Une meilleure compréhension sur la manière dont la structure, la croissance racinaire et l’absorption d’eau répondent au stress nous permettra de mieux comprendre quels sont les aspects de la physiologie racinaire qui contribuent à la tolérance face à la sécheresse. Des recherches précédentes qui s’étaient focalisées sur l’absorption d’eau racinaire chez la vigne ont suggéré que l’absorption d’eau racinaire pouvait être fortement liée à la vitesse de croissance racinaire instantanée (voir Gambetta et al. 2013). Cette observation implique que des différences entre les génotypes dans la résistance face à la sécheresse pourrait largement résulter de leur capacité à maintenir la croissance racinaire en conditions de stress. Deux porte-greffes de vigne avec des capacités contrastées en matière de résistance à la sécheresse, le Riparia Gloire de Montpellier (RGM) et le 110 Richter (110R) ont été sélectionnés pour étudier dans cette thèse. RGM est considéré comme sensible à la sécheresse, tandis que 110R est fortement résistant à la sécheresse (Carbonneau 1985). La thèse a examiné la relation entre la croissance racinaire et la capacité de résistance à la sécheresse en évaluant la vitesse de croissance racinaire, la conductivité hydraulique à travers deux variétés de porte-greffe en conditions de déficit en eau. Le niveau de l’expression des gènes d’aquaporines (via la qPCR et l’ARNseq) et leur contribution à la conductivité hydraulique racinaire ont été analysés dans les radicelles afin d’obtenir une meilleure compréhension sur les mécanismes impliqués dans la régulation de l’absorption de l’eau racinaire et la conductivité hydraulique au cours du développement et en réponse à un manque d’eau.Le traitement de stress d’eau prolongé a diminué le potentiel hydraulique de la plante. La croissance racinaire individuelle est très hétérogène : bien que le traitement de sécheresse réduise l’élongation racinaire en moyenne, la vitesse de croissance racinaire varie tout de même énormément. Un haut niveau de stress hydrique a réduit significativement la vitesse de croissance racinaire moyenne à la fois pour RGM et 110R. Globalement, la vitesse de croissance racinaire moyenne a montré une tendance réduite au cours du développement de la plante. La température du sol est aussi un facteur qui affecte la croissance racinaire. Pour RGM et 110R, en conditionsIIde bon arrosage et de stress hydrique, la vitesse de croissance quotidienne moyenne a été positivement corrélée avec la température du sol quotidienne moyenne. En conditions de bon arrosage, des vitesses de croissance racinaires plus importantes ont été constamment observées chez 110R par rapport à RGM, ce qui pourrait être une explication possible de sa meilleure résistance à la sécheresse par rapport à 110R. [...]The subject of adaptation to climate change has become one of the most important contemporary topics in grapevine. Much focus has been placed on the understanding of rootstocks effects on scion growth, nutrient uptake, and tolerance to stress, with the ultimate goal of developing novel rootstocks that facilitate adaptation to a changing climate. The purpose of this thesis is to examine how differences in drought resistance between genotypes could result largely from differences in their ability to maintain root growth under stress. A better understanding of how root structure, growth, and water uptake respond to stress will allow us to better understand what aspects of root physiology contribute to drought tolerance. Previous research focused on root water uptake in grapevine suggested that root water uptake could be tightly coupled to a root’s instantaneous rate of growth (see Gambetta et al. 2013). This observation implies that differences in drought resistance between genotypes could result largely from their ability to maintain root growth under stress. Two grapevine rootstocks with contrasting drought resistance capacity, Riparia Gloire de Montpellier (RGM) and 110 Richter (110R), were selected to study in this thesis. RGM is considered as sensitive to drought, while 110R is highly resistant to drought (Carbonneau 1985). The thesis examined the relationship between root growth and drought resistant capacity by assessing root growth rate, hydraulic conductivity across two rootstock varieties subjected to water deficit. The role of aquaporin gene expression (via qPCR and RNAseq) and their contribution to root hydraulic conductivity were analyzed in fine roots in order to obtain a better understanding on the mechanisms involved in the regulation of root water uptake and hydraulic conductivity across development and in response to water deficit.Prolonged water stress treatment decreased plant water potential. Individual root growth is very heterogeneous, although drought treatment reduces root elongation on average, individual root growth rate still varies enormously. High level of water stress significantly reduced average root growth rate for both RGM and 110R. Globally, average root growth rate showed a decreased trend over plant development. Soil temperature is also a factor that affects root growth. For both RGM and 110R, under both well-watered and water-stressed conditions, average daily root growth rate was positively correlated with average daily soil temperature. Under well-watered conditions, higher root growth rates were constantly observed in 110R compared to RGM, which could be one possible explanation for the higher capacity in drought resistance of 110R.Root hydraulic conductivity (Lpr) was influenced by both water stress treatment and plant developmental stage. Generally, for both RGM and 110R, Lpr was significantly reduced under water stress in early stage. In mid and late stages, no significant differences in Lpr were observedIVbetween well-watered and water-stressed plants. Changes in individual root Lpr in response to pre-dawn leaf water potential (ᴪpredawn) were investigated as well. Lpr showed a fast drop in the beginning of water stress treatment when ᴪpredawn was higher than -0.5 MPa. However, with ᴪpredawn getting more negative, e.g. from -0.4 MPa to -2.0 MPa, the range of Lpr values measured in our study maintained constant. Lpr of well-watered plants decreased as well even though their ᴪpredawn was maintained at a high level (< 0.1 MPa) during the period of the experiment. [...]
15
Hall, Tavenner Marie. "Evaluating changes in strontium chemistry of stream water in response to environmental stress". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/54408.
Testo completoAbstract (sommario):
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995.Includes bibliographical references (leaves 47-49).
by Tavenner Marie Hall.
M.S.
16
Copeland, Stephen Mark 1955. "Soil water potential as related to the Crop Water Stress Index of irrigated cotton". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276940.
Testo completoAbstract (sommario):
The application of the crop water stress index (CWSI) method to irrigation scheduling is enhanced by knowledge of the relationship between CWSI and soil water potential (SWP) and how this relationship is affected by soil texture. A study using the same cultivar of cotton on three different soils was conducted in southern Arizona over a single growing season. Detailed data were collected of CWSI and soil moisture content for several treatments that scheduled irrigations at threshold CWSI values. CWSI was correlated with soil water potential values calculated from pressure plate determined moisture release curves. Spatial variability of soil characteristics necessitated use of average rather than plot specific moisture release curves. Analysis showed a linear CWSI-SWP relationship that varied greatly with soil depth and study site. The study concluded that soil profile average SWP alone does not normalize the CWSI between sites with different soil textures.
17
Kelly, Harold Lorain Jr 1958. "Remote measurement of turf water stress and turf biomass". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276995.
Testo completoAbstract (sommario):
Increasing irrigation efficiency on turfgrass could help reduce water consumption on large turf facilities. Two experiments were conducted using perennial ryegrass (Lolium perenne (L.) Derby) to evaluate the potential of using remote sensing to estimate turf water status, predict daily evapotranspiration (ET), and estimate turf biomass. In the first experiment a crop water stress index, utilizing remotely sensed canopy temperature, were used to schedule irrigations on 6 of 10 drainage lysimeters. Three of the remaining lysimeters were irrigated used on meteorological estimates of ET calculated using a modified Penman equation. The results of this experiment were inconclusive due to inconsistent lysimeter drainage characteristics. The second experiment was conducted on a turf green with multiple heights to evaluate the potential for using canopy radiance to estimate turf biomass. These results showed that turf biomass could be estimated from a vegetative index (Red Ratio = Near Infrared/Red radiance) obtained through measurements of canopy radiance (r2 = 0.91).
18
Aldakheel, Yousef Yacoub. "Remote sensing of crop water stress : measurements and modelling". Thesis, University of Salford, 1998. http://usir.salford.ac.uk/43021/.
Testo completo
19
NASCIMENTO, MARIA DO PERPETUO SOCORRO CORTEZ BONA DO. "GERMINATION AND ESTABLISHMENT OF THREE TROPICAL LEGUMES (WATER STRESS)". Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184175.
Testo completoAbstract (sommario):
Studies were conducted to test germination and to determine morphological and physiological characteristics of Canavalia obtusifolia DC., Cratylia floribunda Benth. and Dioclea lasiophylla Mart., which allow them to cope with water stress. Germination studies were done using PEG, moist paper and three different soils, in a germinator. Establishment and early growth studies were conducted in a greenhouse, using two different soils. In PEG, maximum percentage germination were near 100% for C. obtusifolia and D. lasiophylla and 75% for C. floribunda. Respectively, the water potentials for maximum germination were from 0 to -1 bar, from 0 to -5 bars, and at -5 bars. In moist paper, however, C. floribunda had near 100% germination. In the three soils, the three species had near or equal to 100% germination and their radicle grew more than in PEG. The rate of germination tended to be faster in soil than in PEG. However, it was affected by both soil and seed characteristics. So, germination was slower in Canelo, a pH 4, clay soil, as well as for the large-seeded C. obtusifolia, may be due to the reduction in the soil water conductivity at the seed-soil interface. It is suggested that leakage of solutes and spoilage of seeds as well as rapid water uptake at high water potentials, resulted in low germination of C. floribunda in PEG. Plants of C. floribunda and D. lasiophylla did not decrease their stomatal conductance or transpiration under high water stress, and their leaf water and osmotic potentials were sharply reduced. Plants of C. obtusifolia partially decreased their stomatal conductance and transpiration under stress. All three species were able to withstand elevated dehydration and to recover after being exposed to leaf water potentials lower than -60 bars. C. obtusifolia maintained net CO₂ assimilation at a high dehydration level (-46.1 bars). After rewetting, this species rapidly recovered its leaf water potential and turgor; its photosynthetic capacity, however, was not totally recovered after being rewetted for six days.
20
Ottman, M. J., S. H. Husman, R. J. Wegener, M. D. Sheedy, K. White e M. T. Rogers. "Critical Growth Stages for Water Stress in Durum, 2001". College of Agriculture, University of Arizona (Tucson, AZ), 2001. http://hdl.handle.net/10150/205410.
Testo completoAbstract (sommario):
The purpose of this research was to determine which durum growth stage is most responsive to additional irrigations (based on 35% depletion) when grown at a slightly suboptimal irrigation level of 65% plant available soil water depletion at other growth stages. A field experiment was conducted at the Maricopa Agricultural Center testing the effects of additional irrigations applied during tillering, jointing, or grain fill. Additional irrigations during tillering, jointing, grain fill, or no additional irrigations resulted in grain yields of 5964, 5419, 6301, and 4200 lbs/acre for Kronos and 5440, 5990, 5030, and 4019 lbs/acre for Westbred 881, respectively. The most responsive stage to additional irrigation was grain fill for Kronos and jointing for Westbred 881. The yield response of Kronos to additional irrigation during jointing may have been reduced by severe (78%) lodging in this treatment.
21
El-Sheikha, Dial-Deen Mohamed. "Remote sensing of water and nitrogen stress in broccoli". Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280349.
Testo completoAbstract (sommario):
Remote sensing is being used in agriculture for crop management. Ground based remote sensing data acquisition system was used for collection of high spatial and temporal resolution data for irrigated broccoli crop. The system was composed of a small cart that ran back and forth on a rail system that was mounted on a linear move irrigation system. The cart was equipped with a sensor that had 4 discrete wavelengths; 550 nm, 660 nm, 720 nm, and 810 nm, and an infrared thermometer, all had 10 nm bandwidth. A global positioning system was used to indicate the cart position. The study consisted of two parts; the first was to evaluate remotely sensed reflectance and indices in broccoli during the growing season, and determine whether remotely sensed indices or standard deviation of indices can distinguish between nitrogen and water stress in broccoli, and the second part of the study was to evaluate remotely sensed indices and standard deviation of remotely sensed indices in broccoli during daily changes in solar zenith angle. Results indicated that nitrogen was detected using Ratio Vegetation index, RVI, Normalized Difference Vegetation Index, NDVI, Canopy Chlorophyll Concentration Index, CCCI, and also using the reflectance in the Near-Infrared, NIR, bands. The Red reflectance band capability of showing stress was not as clear as the previous indices and bands reflectance. The Canopy Chlorophyll Concentration Index, CCCI, was the most successful index. The Crop Water Stress Index was able to detect water stress but it was highly affected by the solar zenith angle change along the day.
22
Stenzel, Fabian. "The implications of large-scale irrigated bioenergy plantations for future water use and water stress". Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://edoc.hu-berlin.de/18452/24078.
Testo completoAbstract (sommario):
Diese Arbeit ist die erste systematische Analyse des globalen Bewässerungsbedarfs für die Bioenergieproduktion des 21. Jahrhundert. In der aktuellen Literatur finden sich diesbezüglich Prognosen von 128,4–9000 km3 yr−1. Die Zahlen hängen stark von den gewählten Parametern und Annahmen sowie den angewandten Methoden und Modellen ab. In systematischen Simulationen für die wichtigsten Parameter mit dem globalen Vegetationsmodell LPJmL, ergeben sich zwei mögliche Pfade um die Erwärmung auf 1.5°C zu begrenzen. Entweder müssten hocheffiziente Bioenergiesysteme entwickelt werden oder es müsste eine unbegrenzte Plantagenfläche bewässert werden dürfen, ohne dabei den Wasserbedarf der Ökosysteme zu berücksichtigen. Letzteres führt zu einem Interessenkonflikt, bei dem die Biomasseproduktion zur Klimarettung auf der einen Seite und der Schutz von Ökosystemen auf der anderen Seite stehen.
Ein weiteres Dilemma wird sichtbar, wenn man den Wasserstress, der sich aus der zusätzlichen Bewässerung ergäbe, mit dem in einer durch ungebremsten Klimawandel um 3°C erwärmten Welt ohne Bioenergie vergleicht: In beiden Szenarien könnte (im Vergleich zu heute) der Wasserstress bis zum Ende des 21. Jahrhunderts stark steigen. Tatsächlich ergäbe sich im Bioenergie-Szenario aber sogar potenziell mehr Wasserstress als im Klimawandel-Szenario. Nachhaltiges Wassermanagement als Kombination aus Wasserentnahmebeschränkungen gemäß den Anforderungen von Flussökosystemen und verbessertem Wassermanagement auf agrarischen Nutzflächen hätte das Potenzial, diesen zusätzlichen Wasserstress zu begrenzen, wäre jedoch auf globaler Ebene schwierig zu etablieren.
Diese Arbeit bestätigt, dass Bioenergieplantagen neben den Negativemissionen, die sie liefern sollen, auch zu unerwünschten Nebenwirkungen in anderen Dimensionen des Erdsystems führen könnten.This thesis provides a first systematic assessment of 21st century global irrigation water demands for bioenergy production, for which the current body of literature projects a range of 128.4–9000 km3 yr−1. The numbers strongly depend on the parameters and assumptions chosen as well as methodologies and models applied. Systematic simulations for the identified key parameters in the dynamic global vegetation model LPJmL yield that even with optimal bioenergy plantation locations, 1.5°C can only be reached in scenarios with highly efficient bioenergy systems or strong irrigation expansion without withdrawal limitations. As a result of the large irrigation requirements, a conflict of interest arises between producing sufficient biomass and protecting environmental flows. A further dilemma is delineated by a comparison of the water stress resulting from the additional irrigation needed to limit climate change and the water stress in a 3°C warmer world without bioenergy. In both scenarios, the global area and the number of people experiencing water stress would increase severely by the end of the 21st century. The bioenergy scenario shows even higher water stress than the case of unmitigated climate change. Sustainable water management, as a combination of water withdrawal restrictions according to environmental flow requirements and improved on-field water management, has the potential to limit this additional water stress. But it would be a challenge to establish such strategies on a global scale. This work confirms that in order to provide large amounts of negative emissions, BECCS might lead to undesired deterioration of our environment and impacts for humanity. It further highlights the dilemma of rising water stress regardless whether climate change or climate change mitigation via irrigated bioenergy become a reality.
23
Lawler, Jennifer Rae Noelle 1962. "Eichhornia crassipes (Mart) Solms in wastewater treatment: Reducing low-temperature stress". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/291651.
Testo completoAbstract (sommario):
Studies were carried out from July 1988 to August 1989 to assess the growth and winter survival of water hyacinth, Eichhornia crassipes (Mart.) Solms, in treatment of secondary domestic wastewater in Tucson, Arizona. Percent of surviving overwintered plants for the following frost protection treatments from November 1988 to March 1989 was: 25 (control), 48 (plastic tarps), 70 (sprinklers), 34 (fog) and 76 (greenhouse). Both control plants and protected plants had longer roots at the effluent end of the ponds than the influent ends during winter months. Greenhouse-protected plants had greater root and entire plant lengths, and greater fresh and dry weights. Dry weight per unit area (kg m⁻²) was higher for greenhouse plants though all protected plants showed decline in dry weight per unit area with temperatures below 10 C. Qualitative observations indicated that protected plants showed less chlorosis and necrosis from low temperatures than control plants, however, plants in all frost protected treatments experienced low temperature stress. Aphids were seen in some of the ponds throughout the study and contributed to severe lamina and petiole damage.
24
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.
Testo completoAbstract (sommario):
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.
25
Lim, Sanghyun. "Sorghum gene expression modulated by water deficit and cold stress". Texas A&M University, 2006. http://hdl.handle.net/1969.1/4705.
Testo completoAbstract (sommario):
Global gene expression in Sorghum bicolor, an important crop showing drought
tolerance in arid and semi-arid cultivated areas, was monitored to exposure of 8-days
seedlings to water deficit (20% polyethylene glycol) or cold stress (4 úC). A sorghum
cDNA microarray, including ~13,000 (milestone version 1) or ~28,000 (milestone
version 2) unigenes, was used to examine gene expression in shoots and roots at 3 and
27hours after stress treatment. ~1,300 and ~2,300 genes were modulated by water deficit
and cold stress, respectively. Up-regulated genes included previously identified stressinduced
genes such as early drought-induced gene, dehydrin, late embryogenesis
abundant gene, glycin and proline-rich gene, and water stress-inducible genes as well as
unknown genes. Genes involved in signal transduction, lipid metabolism, transporter,
and carbohydrate metabolism are induced. Quantitative real-time PCR was used to
quantify changes in relative mRNA abundance for 333 and 108 genes in response to
water deficit and cold stress, respectively. Stress-induced genes were classified by
kinetics. Eighteen of 108 cold-induced genes were modulated by cold but not by ABA and PEG treatment. This research provides the starting point for detailed analysis and
comparison of water deficit and cold modulated gene networks in sorghum.
26
Nuruddin, Molla Md. "Effects of water stress on tomato at different growth stages". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33016.
Testo completoAbstract (sommario):
The study sought to identify the effects of deficit irrigation on the yield and quality of tomatoes. A greenhouse experiment was conducted during the summer of 1999 and repeated in winter 2000 using nine treatments. Two threshold soil moisture deficit levels, 65% and 80% depletion of plant available water, were factorially combined with 5 irrigation timing patterns: (i) no water stress (ii) stress throughout season, (iii) stress during flowering and fruit set, (iv) stress during fruit growth and (v) stress during fruit ripening. The treatments were set up in a randomized complete block design with 4 replicates. Crop yields, maximum and minimum equatorial diameter and fruit heights were measured. The quality parameters included: soluble solids, pH and the color index. Water stress throughout the growing season significantly reduced yield and fruit size but increased the level of soluble solids. No water stress throughout the growing season or stress only during the flowering stage provided highest tomato yield.
27
Abayomi, Yekeen Abiola. "Comparative effects of water stress on wheat and sugar beet". Thesis, Bangor University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304633.
Testo completo
28
Mohammady-D, Shahram. "Inheritance of tolerance to water-stress in wheat (Triticum aestivum)". Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250130.
Testo completo
29
Jacobsen, Anna Linden. "Woody plant adaptations to water stress in arid shrub communities". Diss., Connect to online resource - MSU authorized users, 2008.
Cerca il testo completo
30
Jalali-Farahani, Hamid Reza 1960. "Crop water stress parameters for turfgrass and their environmental dependability". Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/191950.
Testo completoAbstract (sommario):
The concept of crop water stress index (CWSI) was explored using empirical and theoretical models to evaluate bermudagrass water status. The empirical methods were simplifications of the crop energy balance equation. Measured field data were employed to develop the empirical CWSI parameters. Field data were collected from turf plots under three levels of irrigation for the 1986 growing season in Tucson, Arizona. The simplest empirical model of Idso gave the highest variance in estimates of CWSI for all treatments with the estimates being highly influenced by net radiation. An improved empirical model was developed when net radiation was included in the statistical analysis of the canopy temperature minus air temperature limits. In general, the most accurate estimates of CWSI were obtained by using the energy balance equation with constant values of potential canopy and aerodynamic resistances. Various methods were used to evaluate these resistances. Further research is needed to test the perfomance of the theoretically-derived CWSI and to develop more general methods of evaluating the resistances.
31
Osman, Mohamoud, Albert Dobrenz, Haile Tewolde e Robert Voigt. "Stomatal Response to Water Stress in Two Pearl Millet Genotypes". College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/203813.
Testo completoAbstract (sommario):
A study was conducted in the field to test whether stomatal sensitivity to water stress can be used as a selection criterion for drought tolerance in two pearl millet genotypes. In both cultivars, stomatal aperture was significantly reduced by the water stress. However, the proportion of reduction per 20 mm decrease in applied water was much higher for the hybrid than for the female parent. This is clearly an indication of a higher stomatal sensitivity in the hybrid, which probably explains the superior performance under water stress that was previously observed in this genotype.
32
Silvertooth, J. C., S. W. Stedman e J. Tollefson. "Interaction of Pima Cotton Defoliation and Crop Water Stress Index". College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/208291.
Testo completoAbstract (sommario):
A single field experiment was conducted in 1989 to evaluate the relationship of crop water status on Pima cotton defoliation by use of a crop water stress index (CWSI) as estimated by infrared thermometry. The entire study area was given the last irrigation uniformly on 24 August, and 20 row plots were outlined for the arrangement of three treatments in a randomized complete block design with three replications. Treatments consisted of making defoliant chemical application at three different targeted CWSI levels (0.40, 0.60, and 0.85). All defoliant treatments consisted of Dropp plus Accelerate (0.4 lb. and 1.5 pt. of material/acre, respectively) applied with a ground rig applicator. Results indicated no distinct advantage in terms of percent defoliation as a function of lower CWSI levels at which defoliants were applied. The defoliations made at 0.40 CWSI did result in more regrowth after 14 and 21 days. It appears from this test that Pima plants will defoliate satisfactorily with proper chemical treatments up to CWSI levels of 0.80. Further desiccation of the crop results in very erratic CWSI readings, resulting in difficulties in applying this technique to defoliation management. It does appear, though, that Pima cotton defoliation can be accomplished when CWSI readings are between 0.5 and 0.8 without substantial regrowth problems, providing precipitation or irrigation events do not occur.
33
Narváez, Aldáz Christian. "Determination of Prosopis tamarugo Phil. growth response to water stress". Tesis, Universidad de Chile, 2017. http://repositorio.uchile.cl/handle/2250/151048.
Testo completoAbstract (sommario):
Thesis Submitted as part of the requirements for the degree of Master of Science in agricultural sciencesProsopis tamarugo Phil. (tamarugo) is a native legume tree that grows in the Pampa del Tamarugal, Atacama Desert, region of Tarapaca, Chile (Acevedo et al., 1985a). It belongs to the family Leguminosae, subfamily Mimosoideae. Prosopis is a genus with 44 species, of which three are native to Southeast Asia, one to tropical Africa (Galera, 2000) and 40 species are native to America (MINAGRI, 2006). The plants in this genus occupy large areas of soil and diverse climates, from humid subtropical to cold xeric, and from sea level to over 3.000 m altitude (Galera, 2000). In Chile, the genus is represented by 6 species. Prosopis tamarugo is an endemic species that is under threat of extinction, according to the IUCN (International Union for Conservation of Nature) and it is listed as vulnerable in the red book of the conservation status of the Chilean flora (MMA, 2012).
34
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.
Testo completoAbstract (sommario):
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.
35
Lloyd, Jonathan James. "Responses of citrus species to water deficit and salinity stress". Thesis, Adelaide, 1988. http://hdl.handle.net/2440/21660.
Testo completo
36
Lloyd, Jonathan James. "Responses of citrus species to water deficit and salinity stress". Adelaide, 1988. http://hdl.handle.net/2440/21660.
Testo completoAbstract (sommario):
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 1988
37
MARINO, Giovanni, Giovanni MARINO e Giovanni MARINO. "Detection of the effects of water stress on woody plants". Doctoral thesis, Università degli studi del Molise, 2014. http://hdl.handle.net/11695/66250.
Testo completoAbstract (sommario):
Climate change is increasing the chronic water scarcity in many world regions, and also in Mediterranean basin. Water is the most limiting resource for plant growth and development where the climate is characterized by high potential evaporation and low and highly variable rainfall during the growing season. Water deficit constraints all the physiological processes involved in photosynthesis. In addition, drought and heat have effects on plats secondary metabolism as the synthesis and the emission of volatile organic compounds (VOCs) that, on global scale, are able to influence the chemical and physical properties of the atmosphere. Therefore, in last years has become important to develop methods enabling the detection and the description of water relations and the physiological responses of plants experiencing water stress, that could allow the monitoring on large scale of the effects of an increasing drought condition on the vegetation.
In the present study phenotyping methods have been applied to monitor water relations, photosynthetic status and physiological responses in woody plants experiencing water stress. The aim of the study was to evaluate the reliability of remote sensing techniques, based on the passive analysis of spectral reflectance, to monitor the water status of plants and different functions that are affected by drought. Thereafter, a new application of these methods was tested for the detection of the indirect estimation of foliar isoprenoid emissions, in order to sense them remotely. In addition, the relationships and the interactions of chemical and hydraulic signals from root to leaves and the emission of VOCs were investigated in a partial root zone drought experiment on Populus nigra saplings.I cambiamenti climatici in corso stanno aumentando la cronica scarsità di acqua in molte regioni del mondo, come anche nel bacino del Mediterraneo. L'acqua è la principale risorsa limitante per la crescita e lo sviluppo delle piante, in aree in cui il clima è caratterizzato da un elevato potenziale di evaporazione e precipitazioni scarse e molto variabili nel corso delle stagioni vegetative. Il deficit idrico vincola tutti i processi fisiologici coinvolti nella fotosintesi. Inoltre, la siccità e la temperatura hanno anche effetti sul metabolismo secondario delle piante, come la sintesi e l’emissione di composti organici volatili (VOC) che, su scala globale, sono in grado di influenzare le proprietà fisiche e chimiche dell'atmosfera. Pertanto, negli ultimi anni è diventato di rilevante importanza sviluppare metodi che consentano l'individuazione e la descrizione delle relazioni idriche e le risposte fisiologiche delle piante sottoposte a stress idrico, che potrebbero consentire il monitoraggio su larga scala degli effetti della condizione crescente di scarsa disponibilità idrica sulla vegetazione. Nel presente studio sono stati applicati metodi di fenotipizzazione per monitorare le relazioni idriche, lo stato della fotosintesi e le risposte fisiologiche di piante legnose sottoposte a stress idrico. Lo scopo dello studio è stato di valutare l'applicabilità di tecniche di telerilevamento, basate sull'analisi passiva della riflettanza spettrale, per monitorare lo stato idrico e le diverse funzioni di piante legnose sottoposte a siccità. Successivamente, una nuova applicazione di questi metodi è stato impiegata per la stima indiretta delle emissioni fogliari di isoprenoidi, al fine di consentirne il rilevamento da remoto. Inoltre sono stati studiati, in un esperimento in condizione di parziale siccità della zona radicale in piante in vaso di Populus nigra, i rapporti e le interazioni esistenti tra i segnali chimici e idraulici dalle radici alle foglie e l'emissione di VOC.
38
Lama, Rohini. "Biochemical responses of maize (Zea mays L.) to water stress". Thesis, University of North Bengal, 2013. http://ir.nbu.ac.in/handle/123456789/963.
Testo completo
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Wu, Tongyu. "Investigation of the fracture behaviour of epoxy-based water ballast". Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/9574.
Testo completoAbstract (sommario):
The fracture of water ballast tank (WBT) coatings due to thermal stresses is widely recognised as an issue. Upon coating fracture, rapid corrosion of the tanker steel structure will occur, leading to expensive structure repairs or even tanker scrapping. In this project, the fracture behaviour of two experimental WBT coatings, referred to as A and B, in the forms of free film and substrated coatings was investigated. Static tensile tests and fatigue tests of the substrated coatings were performed. A finite element model of coating cracking was developed. Thermal stress and J-integral of surface cracking defects in substrated coatings were calculated using the model, in which the effects of defect size, coating thickness, and thermal strain on coating fracture were investigated. For the first time, fracture mechanics was used to explain WBT coating fracture behaviour. The J-integral of surface defects was used to predict the onset strain of coating cracking under mechanical strains in laboratory and under thermal strains in service. A theoretical comparison between the cracking drive forces in terms of J - integrals in WBT coatings under thermal strains and mechanical strains was performed.
40
Rossler, Ryan Louis. "Water stress effects on the growth, development and yield of sugarcane". Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/40346.
Testo completoAbstract (sommario):
Limited research has been conducted and uncertainty exists regarding sugarcane response to
water stress during different development phases. This information is necessary to optimize
the allocation of limited irrigation water for sugarcane production. The objective of this study
was to understand and quantify the response of crop water use (CWU), canopy development,
stalk elongation, biomass accumulation and partitioning, and sugarcane yield to mild water
stress, imposed through deficit drip irrigation, during different development phases.
A field experiment consisting of a plant and first ratoon crop of cultivar N49 was conducted
near Komatipoort. For the three water stress treatments, available soil water (ASW) was
maintained between 30 and 60% of capacity during the tillering phase (TP), stalk elongation
phase (SEP) and through both phases. ASW was maintained above 60% of capacity in the
well-watered control and during periods when stress was not intended.
Rainfall prevented water stress from developing in the TP of the plant crop. In the ratoon
crop, 72% less irrigation was applied in the TP, resulting in 50 days of stress (ASW<50%).
This did not affect stalk population but reduced CWU by 13%, shortened stalks by 21% and
affected the canopy by reducing green leaf number (GLN) and green leaf area index (GLAI).
Relieving the stress during SEP allowed the crop to re-establish its canopy, capture adequate
photosynthetically active radiation (PAR) and restore rates of photo-assimilation (as
suggested by CWU) and stalk elongation to support rapid biomass production. This
restoration of plant processes allowed the ratoon crop to attain a cane and stalk dry biomass
(SDM) yield that was only 9 and 11% lower (statistically insignificant), respectively, than the
well-watered control at lodging (crop age of 286 days).
During the SEP of the plant and ratoon crop, 42 and 85% less irrigation was applied, resulting
in the crops experiencing 74 and 39 days of stress and using 7 and 8% less water,
respectively. This did not affect stalk population or the crop canopy, but reduced stalk height
by about 6 and 14% in the plant and ratoon crops, respectively. In both crops, shorter stalks
and a negatively affected CWU which reduced photo-assimilate production, reduced cane
yield by 14 and 10% (statically insignificant) and SDM yield by 15 and 5% (statistically
insignificant), in the plant and ratoon crops respectively.
© University of Pretoria
iv
Deficit irrigation throughout the TP and SEP of the ratoon crop reduced irrigation amount by
74%, resulting in 110 days of stress and reducing CWU by 16% and stalk height by 14%.
PAR capture was reduced through reduced GLAI. This resulted in a significant reduction of
15% in cane yield. SDM yield was reduced by 17%, although this was not statistically
significant.
Stalk sucrose content was not influenced by deficit irrigation but was rather dependent on the duration of the drying-off period prior to harvest. Sucrose yields were therefore largely
determined by SDM.
Results suggest that the soil water potential (SWP) measured at 0.25 and 0.40 m depths,
halfway between drip emitters within a plant or ratoon crop, can drop to about -40 kPa before
irrigation is applied, without sacrificing cane or sucrose yield. Lastly, a ratoon crop can
rapidly recover from stress during the TP, provided that the SWP during SEP is maintained
above -40 kPa.Dissertation (MSc Agric)--University of Pretoria, 2013.
gm2014
Plant Production and Soil Science
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41
Gibson, Kelly M. "Water deficit in potato : limitations to photosynthesis in Solanum tuberosum L. cultivars differing in drought tolerance and the impact of reduced cytosolic fructose 1,6 bisphosphatase (FBPase) activity". Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246722.
Testo completo
42
Dzomeku, Israel K. "Modelling seed dormancy, germination and emergence of Striga hermonthica". Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252261.
Testo completo
43
Cole, Jason. "Use of water potential measurements for assessing water stress in Vitis vinifera L. cv. Tempranillo grown in Southern Oregon". Master's thesis, ISA/UL, 2012. http://hdl.handle.net/10400.5/8598.
Testo completoAbstract (sommario):
Mestrado Vinifera EuroMaster - Instituto Superior de AgronomiaA study was conducted to investigate the practical use of four methods for measuring plant water potential (!) of Vitis vinifera L. cv. Tempranillo (syn. Tinta Roriz, Aragónez) under field conditions within the Southern Oregon American Viticultural Area. Predawn leaf water potential (!pd), midday leaf water potential (!l-md), midday stem water potential (!s-md) and early morning stem water potential measured between 07:00h and 08:00h solar time (!s-em) were each measured on vines before and after the initiation of irrigation. Measurements were conducted on the same vines and on the same dates both before and after veraison. Irrigation was applied based on an estimation of vineyard evapotranspiration (ETc) and consisted of four treatments: 70% of ETc continuously (70-70), 35% of ETc continuously (35-35), 70% ETc before veraison and 35% ETc after veraison (70-35) and 35% before veraison and 75% ETc after veraison (35- 70). Irrigation was initiated based on !l-md. When assessing vineyard variability before the initiation of irrigation, with !pd ranging between -0.05 and -0.53, all four measurement types were able to distinguish between high vigor (HV) and low vigor (LV) zones and able to categorize vines under previously established thresholds. However, !l-md showed a tendency to underestimate vine water status at levels greater than -0.9 Mpa. When comparing !s-em, !s-md and !l-md, early morning measurements showed significant differences between irrigation treatments on 3 of 4 measurement dates while midday measurements were able to distinguish significant differences on only 1 of 4 dates. !s-em measurements were generally able to distinguish differences between vine water status even when morning cloud cover was present. Linear regression analysis of !pd versus !s-em, !s-md and !l-md at one site resulted in significant r2 values of 0.62, 0.69 and 0.58, respectively. Linear regression analysis of !s-md versus !l-md using data from both sites resulted in r2 values of 0.88. Overall, !s-em seemed to provide a better option for differentiating plant water status of Tempranillo grapevines in Southern Oregon compared to !s-md and !l-md within the range of water deficit levels studied here. !s-em was able to show differences between the water status of vines before the initiation of irrigation as well as differentiate between irrigation treatments later in the year. However, questions remain about the environmental and physiological factors that might impact the results of this method before water deficit threshold levels can be clearly defined
44
Mardani, Sara, Sayyed Hassan Tabatabaei, Mohammad Pessarakli e Hamid Zareabyaneh. "Physiological responses of pepper plant (Capsicum annuum L.) to drought stress". Taylor & Francis, 2017. http://hdl.handle.net/10150/626132.
Testo completoAbstract (sommario):
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%.
45
Wu, Haoxiang. "Responses of indoor moulds to water dynamics : the transient water conditions rendered by non-24 h air-conditioning". HKBU Institutional Repository, 2020. https://repository.hkbu.edu.hk/etd_oa/798.
Testo completoAbstract (sommario):
Due to rapid urbanisation, people in metropolises spend the majority of their time indoors. Indoor mould contamination, as one of the most pungent biohazards in built environments, can ubiquitously present in humid areas and potentially compromise the health of occupants. Governmental institutions like the World Health Organisation and United States Environmental Protection Agency have put forward guidelines for indoor mould prevention. However, these guidelines normally require occupants to maintain a low indoor humidity (<75% or even 40%), and thus, in tropical and subtropical areas, one of the most widely used approaches to prevent indoor mould contamination is to continuously operate air-conditioners or dehumidifiers (AC/D). The 24 h operation of AC/D, however, conflicts with the requirement of energy sustainability, and hence posits a trade-off between sustainability and indoor mould hygiene. The aim of this study was to facilitate the development of sustainable and effective mould prevention strategies for indoor environments. The literature on currently adopted mould prevention strategies including that target moisture (24 h AC/D), temperature (air-conditioning system and cool wall paint) and nutrient (dust removal) elements as well as new nanoparticles technology (Ag, TiO 2 and MgO nanoparticles), was reviewed and the main limitations of these strategies were discussed. It was found that none of these current mould prevention measures has addressed both sustainability and mould hygiene on balance, urging further investigations. Therefore, the objective of the first phase investigation was to develop sustainable cause-specific mould control measures in built environments. A case study of a mould contaminated site was conducted to illustrate the micro-environments that contribute to mould contamination in buildings. The currently used 24-h AC/D approach was compared with and ranked against other sustainable alternatives. The results of this case study suggest that determining an effective non-24 h AC/D management regime tends to be a sustainable and user-friendly solution. To develop such a regime, understanding the critical mechanisms regulating indoor mould responses to water dynamics is essential. Thus, the objective of the second phase was to characterise the critical mechanism regulating the growth of common indoor moulds under water dynamics. It was hypothesised that oxidative stress is associated with the growth of indoor moulds under water dynamics. Using Cladosporium cladosporioides as a model, both its pre-germination and germinated spores were exposed to daily wet-dry cycles. Afterwards, the growth was assessed and cellular H 2 O 2 concentration and catalase activity were measured. It was found that under water dynamics, the longer growth delay in C. cladosporioides was associated with a higher encountered oxidative stress, with 12-12 wet-dry cycle (12 h wet, 12 h dry) showing the longest delay and highest oxidative stress. Pearson correlation and linear regression analysis suggest a positive correlation between growth delay and oxidative stress under water dynamics (R 2 =0.85, P<0.0001). Moreover, pre- germination spores generally exhibited shorter growth delay, lower cellular H 2 O 2 concentration and higher catalase activity. Collectively, these results suggest that the growth of C. cladosporioides is associated with oxidative stress under water dynamics. After revealing the association between the growth of C. cladosporioides and oxidative stress under water dynamics, at the third phase, this finding was extrapolated to different mould species (C. cladosporioides, Aspergillus niger and Aspergillus penicillioides), water activity (a w ) (0.4 a w , 0.6 a w and 0.8 a w ) and temperature levels (19 °C and 28 °C). In addition, the antioxidant responses of treated moulds, including antioxidant enzymes (superoxide dismutase, catalase, glutathione reductase and glutathione peroxidase) were monitored. The results showed that lower water activity levels imposed higher oxidative stress to moulds, and A. penicillioides exhibited the highest tolerance which displayed the highest antioxidant activities and encountered lowest oxidative damage under water dynamics. Moreover, no significant difference was measured in terms of the survival, oxidative stress and antioxidant responses between these two temperature levels. The third phase of the study, for the first time discovered the reason contributing to the different resistance towards water dynamics among common indoor moulds, and further confirmed the important role of oxidative stress adaptation in withstanding transient water supply. In conclusion, this study reveals the critical role of oxidative stress adaptation in helping moulds to cope with changing water conditions, which may shed light on a new perspective for the future development of indoor mould prevention strategies. It also indicates that longer operation time of AC/D each day may not necessarily lead to better prevention of mould contamination, suggesting that in order to sustainably prevent mould contamination, one should operate reasonable non-24 h AC/D each day (12 h/day according to the examined species in this study) to yield a more stressful wet-dry cycle to moulds. The outcomes of this study foster the development of novel and sustainable indoor mould prevention strategies
46
Metzler, F., S. Husman e R. Wegener. "Lint Yield Response to Varied Levels of Water Stress and Consumptive Water Use Requirements of Upland Cotton". College of Agriculture, University of Arizona (Tucson, AZ), 1997. http://hdl.handle.net/10150/210946.
Testo completoAbstract (sommario):
Lint yield response to varied Management Allowed Depletion Levels (MADL), and consumptive water use rates were determined for four upland cotton varieties (D&PL 5415, D&PL NuCotn 33B, D&PL 5816, and STV 474) at the Maricopa Agricultural Center. Four irrigation treatments based on MADL of 35% (Very Wet), 50% (Wet), 75% (Medium) and 90% (Dry) of available moisture were used to schedule irrigations after May 16. The Very Wet and Wet treatments showed statistically similar yields which were much greater than the Medium and Dry treatments. Irrigation return intervals of six to ten days from early June thru late July appeared to provide the greatest lint yields. Consumptive water use appears to reach its maximum during the peak bloom period of the fruiting cycle. Following peak bloom, water use gradually diminishes.
47
Fangmeier, D. D., S. H. Husman e D. J. Jr Garrot. "Irrigation Scheduling Based on the Crop Water Stress Index and Precision Water Application for High Cotton Yield". College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/219764.
Testo completoAbstract (sommario):
The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.A modified, low- pressure linear move irrigation system was used to irrigate cotton at the Marana Agricultural Center, University of Arizona in 1985. Irrigations were scheduled using the Crop Water Stress Index (CWSI) for timing and a neutron probe to determine soil moisture deficits. Irrigations were applied when the CWSI reached 0.1 resulting in minimal seasonal water stress. Yields ranged from 3.14 bales /acre to 2.73 bales/acre from 2 acre plots. Total applied water ranged from 31.3 inches to 32.3. Total seasonal rainfall was 2.90 inches.
48
Li, Guangfu. "The performance of transition joints in high temperature water environments". Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362413.
Testo completo
49
Mbave, Zwidofhelangani Aubrey. "Water stress effects on growth, yield and quality of wheat (Triticum aestivum L.)". Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/24146.
Testo completoAbstract (sommario):
Understanding the effects of water stress on wheat growth, yield and quality is essential for good irrigation management. In South Africa most of the wheat production areas are vulnerable to drought stress during crop development. That causes substantial reduction in grain yield, depending on the developmental stage at which water stress occurred. Supplemental irrigation is the main strategy for adaptation and stabilisation of yield under water stress. However, agriculture is the leading single water-use sector locally, consuming about 60% of total available water. Therefore, the need to improve water use efficiency (WUE) in crop production is clear, since South Africa is classified as a water-scarce country. Experiments were conducted under a rain shelter at Hatfield Experimental Farm, University of Pretoria, in the 2010 and 2011 seasons. The main objective of the study was to evaluate the effects of water stress at different stages on growth, yield, and quality of three wheat cultivars, namely Duzi, Steenbras and SST 843. Water stress was imposed by withholding water at either of three growing stages. The first treatment was stressed during tillering stages to flag leaf (stem elongation (SNN)), followed by water stress from flag leaf to the end of flowering (flowering stage (NSN)), and lastly water stress from grain filling to physiological maturing (grain-filling stage (NNS)), whereas optimal supply of water was maintained throughout the season by weekly irrigating to field capacity for the control treatment (NNN). Irrigation treatments and cultivars influenced growth, yield and quality, depending on the developmental stage at which irrigation was withheld. The control treatment (NNN) and the treatment stressed in the flowering stage (NSN) had highest and lowest grain yield respectively in both seasons. Water stressed treatment NSN reduced grain yield by 33% and 35% in the 2010 and 2011 seasons respectively, when compared with the control treatment (NNN). Reduction of grain yield due to stress in the flowering stage (NSN) was ascribed to reduction in the number of seeds per ear, number of ears per unit area, ear length, and flag-leaf photosynthesis rate (Pn). In the flowering stage (NSN) water stress reduced Pn by 59% which was due to increased leaf temperature because of lower transpiration (E) and stomatal conductance (gs). The water stress treatment NSN reduced transpiration by 72% and stomatal conductance by 84% in the flowering stage. Plant height was reduced by 23% because of water stress imposed in the flowering stage (NSN), which consequently decreased biomass yield by 29% in the 2011 season. Growth and yield parameters showed dramatic recovery when stress was terminated during the flag-leaf stage (SNN). The cultivar Steenbras had lower yield reduction under stress, whereas Duzi and SST 843 had higher yield potential under the well-watered conditions (NNN). In the 2011 season SST 843 had higher WUE of 14.2 kg ha-1 mm, which corresponded to higher grain yield of 7210 kg ha-1 and higher ET of 509 mm. Water-stress treatment SNN gave the highest WUE of 14.9 kg ha-1 mm, which corresponded to a total water use (ET) of 451 mm and grain yield of 6738 kg ha-1. Water stress treatments SNN and NNS reduced ET by 27% and 17%, respectively, which translated to 173 mm and 105 mm water saved by each treatment correspondingly. Grain protein content (GPC) was reduced most by the treatment exposed to stress in the stem elongation stage (SNN). However, the GPC was acceptable (>12%) in all treatments in both seasons. Hectolitre mass was reduced most by water stress imposed during grain filling (NNS). Water stress treatment NNS lowered the hectolitre mass by 3% and 4% in the 2010 and 2011 seasons respectively. Generally all quality parameters in the present study were acceptable for all irrigation treatment and cultivars. The hypothesis that water stress in the stem elongation and grain-filling stages will have little effect on yield and improve WUE was accepted. Therefore it can be recommended that supplemental irrigation should be applied from flag leaf to end of flowering (NSN) stages of wheat in order to minimise grain yield losses in the absence of rainfall. Further research should focus on extrapolation of these results to other production regions using crop models.Dissertation (MInstAgrar)--University of Pretoria, 2013.
Plant Production and Soil Science
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50
Che-Haron, Ismail. "Nutrient uptake of three grass species in relation to water stress". Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46709.
Testo completo