Submitted by (lucia.rodrigues@ufrpe.br) on 2016-08-31T10:53:10Z No. of bitstreams: 1 Maria Alice Vasconcelos da Silva (1).pdf: 762537 bytes, checksum: c100c2c556639aa3d440082da1ef7bb5 (MD5) / Made available in DSpace on 2016-08-31T10:53:10Z (GMT). No. of bitstreams: 1 Maria Alice Vasconcelos da Silva (1).pdf: 762537 bytes, checksum: c100c2c556639aa3d440082da1ef7bb5 (MD5) Previous issue date: 2007-08-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work aimed to study the effect of water deficit on gas exchange, leaf water potential, dry matter production, and some biochemical aspects of Schinus terebinthifolius Raddi. young plants. A research project was developed, under greenhouse conditions, at the Laboratório de Fisiologia Vegetal, Departamento of Biologia of Universidade Rural de Pernambuco between November, 2005 to February, 2006. Seedlings with 3 month-old and sexually propagated were cultivated in containers containing 5.5 kg of soil. The entirely randomized experimental design was used, with four water treatments (100%, 75%, 50% and 25% to field capacity-FC), with four replicates. Plants under 25% FC were re-watered to 100% FC once after stomatal closure. After 15 days of acclimation period have started the water treatments. The experimental period lasted for 74 days. Transpiration (E), diffusive resistance (Rs), leaf temperature (Tfol), air temperature (Tar), relative humidity of the air (UR), photosynthetically active radiation (PAR), and vapor pressure deficit (VPD) were evaluated at midday each seven days. At the end of the experimental period, leaf water potential (Yf) was measured at midday. Leaves (LDM), stems (SDM), roots (RDM), and total dry masses (TDM), root to shoot ratio (R/Sh), and leaves (LBA), stems (SBA) and roots biomass allocation (RBA) were determined. In addition, carbohydrates, free proline, soluble protein and free amino acids contents were analyzed. In plants under 25% field capacity, stomatal closure was observed after 11 days of water treatments. At the time plants were re-watered to 100% FC. After 24 h plants re-watered recovered the stomatal aperture, which remained open until the end of the experimental period. Water deficit decreased the leaf water potential (Yf) in plants grown at 25% FC (-2.2 MPa) when compared with the 100% FC treatment (-1.1 MPa). Plants grown under 75% FC producted higher LDM, SDM and RDM than the other treatments. Differences among treatments to biomass allocation were not observed, but there was a tendency to plants grown under 25% of FC to increase more biomass allocation than the other treatments. The water stress reduced carbohydrates contents and increased soluble protein and amino acids. However, differences to proline content were not verified among water treatments. These results suggest that this species is tolerate to low humidity levels in the soil and that the level of 75% of FC is the best to cultivate it in the initial fase of development. / Com o objetivo de estudar os efeitos do déficit hídrico sobre as trocas gasosas, o potencial hídrico foliar, a produção de matéria seca e alguns aspectos bioquímicos de plantas jovens de Schinus terebinthifolius Raddi, foi desenvolvido um trabalho em casa de vegetação do Laboratório de Fisiologia Vegetal do Departamento de Biologia da Universidade Federal Rural de Pernambuco, no período de novembro de 2005 a fevereiro de 2006. Utilizaram-se mudas com três meses de idade, propagadas sexuadamente, as quais foram transferidas para vasos de polietileno contendo 5,5 kg de solo. Adotou-se um delineamento experimental inteiramente casualizado, representado por quatro tratamentos hídricos (100% da Capacidade de pote; 75% CP; 50% CP; 25% CP) com quatro repetições. Após 15 dias sob aclimatação, procedeu-se o início dos tratamentos hídricos. Durante o período experimental foram efetuadas medições das trocas gasosas do vapor d’água às 12 horas em intervalos de 7 dias. Avaliou-se a transpiração (E), a resistência difusiva (Rs), a temperatura foliar (Tf), a temperatura do ar (Tar), a umidade relativa do ar (UR), a radiação fotossinteticamente ativa (RFA) e o déficit de pressão de vapor (DPV). No final do período experimental foi mensurado o potencial de água da folha (Yf) às 12 horas e determinado o peso da matéria seca das folhas (MSF), dos caules (MSC), das raízes (MSR), a matéria seca total (MST), a relação raiz/parte aérea (R/Pa) e a alocação de biomassa para as folhas (ABF), caules (ABC) e para as raízes (ABR). Além disso, foram analisados os teores de carboidratos, de prolina livre, proteínas solúveis e aminoácidos livres. O fechamento estomático ocorreu em plantas submetidas a 25% CP, aos 11 dias após a diferenciação dos tratamentos hídricos quando as plantas foram reirrigadas para 100% CP. Após 24 horas houve recuperação da abertura estomática mantendo-se até o final do experimento. O déficit hídrico reduziu o potencial hídrico foliar (Yf) nas plantas do tratamento estresse moderado (–2,2 MPa) quando comparado com o controle (-1,1 MPa). As plantas do tratamento 75% CP se destacaram em relação aos demais tratamentos, por produzirem mais matéria seca para as folhas (MSF), caule (MSC) e raízes (MSR). Com relação à alocação de biomassa, não houve diferença significativa entre os tratamentos, porém houve uma tendência do tratamento 25% CP alocar mais biomassa para do que os demais tratamentos. Em relação aos solutos orgânicos, o déficit hídrico provocou reduções nos teores de carboidratos e aumento no teor de proteínas e aminoácidos, não havendo diferença entre os tratamentos para os teores de prolina. Os resultados sugerem que a aroeira é tolerante a baixos níveis de umidade no solo e que o nível de 75%CP é o mais indicado para o cultivo desta espécie na fase de muda.

Dans un contexte de changements climatiques, le stress hydrique et la gestion de l'eau sont considérés comme une contrainte importante pour le secteur agricole. Ainsi la sélection pour la tolérance à la sécheresse est devenue un objectif majeur pour de nombreux programmes de sélection. La vulnérabilité à la cavitation est considérée comme un trait d'intérêt pour la sélection à une sécheresse extrême, en particulier pour les plantes ligneuses. Pourtant, l'étendue de sa variabilité et sa relation avec la tolérance à la sécheresse sont mal documentées à l’échelle intra-spécifique, et en particulier dans les espèces cultivées. Dans cette étude, la variabilité génétique de la vulnérabilité à la cavitation a été étudiée sur trois dispositifs expérimentaux différents avec trois arbres d’intérêt agronomique qui sont menacés par le risque de sécheresse: noyer, hévéa et pommier. Une faible ou aucune, variation de la vulnérabilité à la cavitation a été trouvée dans les espèces étudiées ainsi qu'entre deux espèces de noyers malgré les différences de traits précédemment rapportés. Ces résultats suggèrent une canalisation de la résistance à la cavitation dans les organes critiques (branches, tiges). Chez le pommier, le porte-greffe est soupçonné de provoquer de la plus étroite résistance à la cavitation sur le greffon. Par contre, des différences ont bien étés trouvées sur d’autres traits de réponse à la sécheresse comme la régulation stomatique, la chute des feuilles ou encore la vulnérabilité à la cavitation dans le pétiole. Ainsi, la vulnérabilité à la cavitation des organes critiques n’est pas un paramètre pertinent pour la sélection de la tolérance à la sécheresse, et les programmes de sélection sur les espèces étudiées ne semblent pas avoir affecté ce paramètre. / In a context of climatic changes, drought stress and water management are regarded as one of the most important constraints for agricultural sector. Thus the selection for drought tolerance became a main objective for many breeding programs. Vulnerability to cavitation is considered a trait of interest for the selection for extreme drought stress, especially for woody species. However, the extent of its variability and its relation to drought tolerance are poorly documented on intraspecific level, particularly for cultivated species. In this study the genetic variability of vulnerability to cavitation was studied on three different experimental devices with three trees of agronomic interest that are threatened by the risk of drought: walnut, rubber and apple trees. Low or no variation in xylem vulnerability to cavitation was found in the studied species and between two species of walnuts despite differences previously reported features. These results suggested a canalization of cavitation resistance on critical organs (branches and stems). In apple tree, the rootstock was suspected to cause the narrow resistance to cavitation on the scion. On the contrary, differences on other traits in response to drought stress such as stomatal regulation, leaf shedding or vulnerability to cavitation on petiole were found. Therefore, vulnerability to cavitation of critical organs was not a relevant parameter for the selection of drought tolerance and breeding programs on the species studied did not appear to affect this parameter.

Le potassium (K) est un élément majeur connu pour contribuer à la résistance des plantes à la sècheresse. L'étudede son influence sur la réponse physiologique du maïs (Zea mays L.) sous contrainte hydrique est essentiellepour prédire la future productivité dans un contexte de changements climatiques, en particulier de la diminutiondes précipitations. Des modalités d'apports en K et en eau ont été croisées et soumises à des plants de maïs,élevés en condition contrôlées ou cultivés au champ. La croissance (biomasses aériennes et racinaires,rendements en grain) ainsi que les mécanismes écophysiologiques du métabolisme carboné (photosynthèse,transport des sucres) et du statut hydrique (transpiration, conductance stomatique, potentiels hydriques) ont étéétudiés. L'apport de K a contribué à l'augmentation de la croissance, le développement et le rendement grain quelque soit le régime hydrique imposé au maïs et les conditions d'expérimentation. Les résultats attendus sur lameilleure régulation stomatique en cas de déficit hydrique sont moins évidents. L'effet du stress hydrique ou dela déficience en K tendent à diminuer la photosynthèse. Cependant, ces effets ressortent plus sur les feuillesâgées que sur les feuilles jeunes. Dans ces mêmes conditions, le transport des sucres ne semble pas être unélément limitant de la croissance. Plusieurs résultats convergent pour attribuer au K un rôle dans la maîtrise despertes en eau (par unité de surface foliaire) et sur la meilleure efficience d'utilisation de l'eau. Néanmoins, cetteefficience est imputée à des meilleurs rendements, liés à une surface foliaire plus importante, et non pas à unemoindre consommation de l'eau. / Potassium (K) is a major nutrient known to help plants resist drought. In the context of climate change,quantifying the role of K on maize physiological acclimation to reduced precipitations is essential to betterpredict future productivity. Maize (Zea mays L.) plants grown under controlled or field conditions weresubmitted to different K and water levels. Plant growth (shoot and root biomass, grain yield) as well as plantwater status (transpiration, stomatal conductance, water potential) and ecophysiological mechanisms of Carbonmetabolism (photosynthesis, sugar transport) were studied. Regardless of the water regime and experimentalconditions, K nutrition increased growth and whole-plant development and improved grain yield. The effect ofwater stress on stomatal regulation was not straightforward and depended on the level of K fertilization. Theeffects of water or K deficit tend to decrease photosynthesis. Drought or K nutrition affected more leafphotosynthesis in old than in young leaves, and sugar transport did not seem to be a growth limiting factor. Ourresults demonstrated a strong effect of K on biomass production and a higher water use efficiency with less of animpact on leaf-level physiology. This better water use was mainly the consequence of the positive effect of leafarea on yield, and not due to a reduce water use.

Introducing effective irrigation management in arid and semi-arid regions, like most areas of South Africa, is an indispensable way of maximising crop yield and enhancing productivity of scarce freshwater resources. Holistic improvements in agricultural water management could be realised through integrating the knowledge of crop-specific water requirements. In order to develop effective irrigation schedules for rose-scented geranium (Pelargonium capitatum x P. radens), greenhouse and field experiments were conducted at the Hatfield Experimental Farm of the University of Pretoria, Pretoria, South Africa, from 28 October 2004 to 2006. Results from 20, 40, 60 and 80% maximum allowable depletion (MAD) levels of the plant available soil water (ASW) indicated that plant roots extracted most of the soil water from the top 40 cm soil layer, independent of the treatment. Both essential oil yield and fresh herbage mass responded positively to high soil water content. Increasing the MAD level to 60% and higher resulted in a significant reduction in herbage mass and essential oil yields. An increase in the degree of water stress apparently increased the essential oil concentration (percentage oil on fresh herbage mass basis), but its contribution to total essential oil yield (kg/ha oil) was limited. There was no significant relationship between MAD level and essential oil composition. For water saving without a significant reduction in essential oil yield of rose-scented geranium, a MAD of 40% of ASW is proposed. Response of rose-scented geranium to a one-month irrigation withholding period in the second or third month of regrowth cycles showed that herbage mass and oil yield were positively related. Herbage yield was significantly reduced when the water stress period was imposed during the third or fourth month of regrowth. A remarkable essential oil yield loss was observed only when the plants were stressed during the fourth month of regrowth. Essential oil content (% oil on fresh herbage mass basis) was higher in stressed plants, especially when stressed late, but oil yield dropped due to lower herbage mass. The relationship between essential oil composition and irrigation treatments was not consistent. Water-use efficiency was not significantly affected by withholding irrigation in the second or in the third month of regrowth. With a marginal oil yield loss, about 330 to 460 m3 of water per hectare per regrowth cycle could be saved by withholding irrigation during the third month of regrowth. The overall results highlighted that in water-scarce regions withholding irrigation during either the second or the third month of regrowth in rose-scented geranium could save water that could be used by other sectors of society. In greenhouse pot experiments, rose-scented geranium was grown under different irrigation frequencies, in two growth media. Irrigation was withheld on 50% of the plants (in each plot) for the week prior to harvesting. Herbage and essential oil yields were better in the sandy clay soil than in silica sand. Essential oil content (% oil on fresh herbage mass basis) apparently increased with a decrease in irrigation frequency. Both herbage and total essential oil yields positively responded to frequent irrigation. A one-week stress period prior to harvesting significantly increased essential oil content and total essential oil yield. Hence, the highest essential oil yield was obtained from a combination of high irrigation frequency and a one-week irrigation-withholding period. In the irrigation frequency treatments, citronellol and citronellyl formate contents tended to increase with an increase in the stress level, but the reverse was true for geraniol and geranyl formate. Leaf physiological data were recorded during the terminal one-week water stress in the glasshouse pot trial. Upon rewatering, stomatal conductance (Gs) and transpiration rate (Rt) were significantly lower in the less often irrigated than in the more often irrigated treatments, while leaf water potential (yw) and relative water content (RWC) were the same for all plants, indicating that water stress had an after-effect on Gs and Rt. At the end of the stress period, Gs, Rt, yw and RWC were lower in the plants from the more often irrigated than from the less often irrigated treatments. Irrespective of irrigation treatment, one type of non-glandular and two types (different in shape and size) of glandular trichomes were observed. In water stressed-conditions, stomata and trichome densities increased, while the total number of stomata and trichomes per leaf appeared to remain more or less the same. Water stress conditions resulted in stomatal closure. / Thesis (PhD)--University of Pretoria, 2009. / Plant Production and Soil Science / unrestricted

Hydrological processes and dynamics in the changing climate and environment: Lessons learned from multiple temporal and spatial scales Ye Su ABSTRACT Climate change, along with the changes in land use and land cover (LULC), is the key factor driving the changes in hydrological processes and dynamics in a basin. This thesis emphasized on understanding the impact of both long-term climate change and abrupt anthropogenic driven agricultural intensification or natural driven insect-induced forest disturbance on hydrological processes and dynamics at varying spatial and temporal scales in two diverting terrestrial environment. Two pattern-based investigations, one case study in a forest region in Central Europe and another in a semi-arid region in Central Asia, were aimed to answer the main research question "what are the responses of hydrological dynamics and the related hydro-geochemical conditions to climate change and certain changes in LULC at a basin-scale?". The long-term hydro-climatic dataset was used for conducting statistical analyses and establishing hydro-climatic modelling at the basin scale. We further conducted process-based studies, attempting to understand how and why the specific hydrological dynamics were altered at smaller spatial and temporal scales: (i) a catchment-scale tracer-based...

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[Truncated abstract. Please see the pdf format for the complete text. Also, formulae and special characters can only be approximated here. Please see the pdf version for an accurate reproduction.] This thesis examines the water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on bauxite mine rehabilitation sites in the jarrah forest of south-western Australia. The principal objective was to characterise the key environment and plant-based influences on tree water use, and to better understand the dynamics of water use over a range of spatial and temporal scales in this drought-prone ecosystem. A novel sap flow measurement system (based on the use of the heat pulse method) was developed so that a large number of trees could be monitored concurrently in the field. A validation experiment using potted jarrah saplings showed that rates of sap flow (transpiration) obtained using this system agreed with those obtained gravimetrically. Notably, diurnal patterns of transpiration were measured accurately and with precision using the newly developed heat ratio method. Field studies showed that water stress and water use by jarrah saplings on rehabilitation sites were strongly seasonal: being greatest in summer when it was warm and dry, and least in winter when it was cool and wet. At different times, water use was influenced by soil water availability, vapour pressure deficit (VPD) and plant hydraulic conductance. In some areas, there was evidence of a rapid decline in transpiration in response to dry soil conditions. At the end of summer, most saplings on rehabilitation sites were not water stressed, whereas water status in the forest was poor for small saplings but improved with increasing size. It has been recognised that mature jarrah trees avoid drought by having deep root systems, however, it appears that saplings on rehabilitation sites may have not yet developed functional deep roots, and as such, they may be heavily reliant on moisture stored in surface soil horizons. Simple predictive models of tree water use revealed that stand water use was 74 % of annual rainfall at a high density (leaf area index, LAI = 3.1), high rainfall (1200 mm yr-1) site, and 12 % of rainfall at a low density (LAI = 0.4), low rainfall (600 mm yr-1) site, and that water use increased with stand growth. A controlled field experiment confirmed that: (1) sapling transpiration was restricted as root-zone water availability declined, irrespective of VPD; (2) transpiration was correlated with VPD when water was abundant; and (3) transpiration was limited by soil-to-leaf hydraulic conductance when water was abundant and VPD was high (> 2 kPa). Specifically, transpiration was regulated by stomatal conductance. Large stomatal apertures could sustain high transpiration rates, but stomata were sensitive to hydraulic perturbations caused by soil water deficits and/or high evaporative demand. No other physiological mechanisms conferred immediate resistance to drought. Empirical observations were agreeably linked with a current theory suggesting that stomata regulate transpiration and plant water potential in order to prevent hydraulic dysfunction following a reduction in soil-to-leaf hydraulic conductance. Moreover, it was clear that plant hydraulic capacity determined the pattern and extent of stomatal regulation. Differences in hydraulic capacity across a gradient in water availability were a reflection of differences in root-to-leaf hydraulic conductance, and were possibly related to differences in xylem structure. Saplings on rehabilitation sites had greater hydraulic conductance (by 50 %) and greater leaf-specific rates of transpiration at the high rainfall site (1.5 kg m-2 day1) than at the low rainfall site (0.8 kg m-2 day1) under near optimal conditions. Also, rehabilitation-grown saplings had significantly greater leaf area, leaf area to sapwood area ratios and hydraulic conductance (by 30-50 %) compared to forest-grown saplings, a strong indication that soils in rehabilitation sites contained more water than soils in the forest. Results suggested that: (1) the hydraulic structure and function of saplings growing under the same climatic conditions was determined by soil water availability; (2) drought reduced stomatal conductance and transpiration by reducing whole-tree hydraulic conductance; and (3) saplings growing on open rehabilitation sites utilised more abundant water, light and nutrients than saplings growing in the forest understorey. These findings support a paradigm that trees evolve hydraulic equipment and physiological characteristics suited to the most efficient use of water from a particular spatial and temporal niche in the soil environment.