Stomatal development and its regulation by environmental conditions (light, CO2 concentration) and physiological processes in the leaf of higher plants were investigated. The study was based on the assumptions that stomatal development should be regulated by signals coming from both external environment and leaf interior, and that the signal should be transduced from cotyledons to leaves. Transgenerational effect in stomatal development was also studied. Molecular and physiological approaches were applied to reveal the relationship between leaf environment, stomatal development, stomatal function and leaf physiology.

Orientador: Luiz Fernando Rolim Almeida / Resumo: Espera-se que os efeitos da seca aumentem e alterem a duração do estresse hídrico nos próximos anos em diferentes regiões agrícolas. A recuperação fisiológica após o estresse hídrico ainda não é compreendida e as aquaporinas (AQPs) participam do processo de recuperação. Nosso objetivo foi avaliar se as aquaporinas estão associadas com o processo de recuperação fisiológica nas folhas após a reidratação. Plantas de Sorghum bicolor L. (Moench) foram submetidas a diferentes intensidades de estresse hídrico durante 20 dias e posterior reidratação durante 12 dias. Durante estes períodos, as variáveis de relações hídricas, fluorescência da clorofila a, trocas gasosas e a expressão dos genes PIP1,5, PIP2;2 e TIP1; 1 foram avaliados. Plantas submetidas ao déficit hídrico moderado (DHM) mostraram mesmos valores do controle em todas as variáveis fisiológicas e aumento da expressão das aquaporinas no final do déficit hídrico. Enquanto as plantas da deficiência hídrica severa (DHS) e severa progressiva (DHSP) apresentaram diminuição nas variáveis de relações hídricas, limitação estomática e não estomática da fotossíntese e baixa expressão das aquaporinas. Após a reidratação, as plantas desses tratamentos apresentam conjunto de ajustes fisiológicos que permitem o retorno da fotossíntese 144 horas após o fornecimento de água, sendo a limitação estomática a maior responsável pela recuperação. As AQPs analisadas são responsivas à reidratação somente nas plantas que não tiveram controle da rep... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: It is expected that the effects of drought increase and change the duration of water stress in the coming years in different agricultural regions. The physiological recovery after water stress is still not well understood and aquaporins (AQPs) participate in the recovery process. Our aim was evaluate whether aquaporins are associated with physiological recovery process in leaves after rehydration. Sorghum bicolor L. (Moench) plants were submitted to different intensities of water stress during 20 days and subsequent rehydration for 12 days. During these periods, variables of water relations, chlorophyll fluorescence, gas exchange and PIP1;5, PIP2;2 and TIP1;1 gene expression were evaluated. Moderate water deficit (DHM) plants showed same values of control in all physiological variables and increased aquaporins expression in the end of water deficit. While severe (DHS) and progressive severe water stress (DHSP) plants had decreased water relations, diffusive and non-diffusive limitation of photosynthesis and low aquaporins expression. After rehydration, plants of these treatments have set of physiological adjustments that enable the return of photosynthesis 144 hours after the water supply. Stomatal limitation was the most responsible for recovery. The AQPs analyzed are responsive to rehydration only in plants that did not have control of water replacement in the soil (DHSP). We observed a pattern of responses of these AQPs that depends on the intensity of water deficit and no... (Complete abstract click electronic access below) / Mestre

Realizaram-se campanhas em árvores de cinco anos de idade de Pinus caribaea var. hondurensis e Pinus taeda em parcelas controle (sem fertilização e sem irrigação) e parcelas fertilizadas e irrigadas, durante o verão e o inverno de 2012 visando caracterizar as seguintes variáveis fisiológicas: i) Capacidade máxima fotossintética (Amax); ii) Fotossíntese ao longo do dia (A); iii) Variação da condutância estomática (gs) em relação ao aumento do déficit de pressão de vapor (DPV); e iv) Taxas máximas de carboxilização (Vcmax) e de transporte de elétrons (Jmax) via curvas A/Ci. O estudo foi realizado no projeto Produtividade Potencial do Pinus no Brasil, localizado na Estação Experimental da ESALQ/USP em Itatinga-SP.Foram escolhidas três árvores médias por parcela para as avaliações fisiológicas, realizadas com o LiCor 6400XT. A mensuração da Amax foi realizada no terço médio da copa, em dois galhos por árvore e em duas posições por galho, sendo realizada das 8 às 10 horas, e o comportamento da A, gs com o aumento do DPV, ocorreram de hora em hora, das 11 às 15 horas. Ao final, as acículas foram coletadas para a determinação da área foliar específica (AFE) e do nitrogênio foliar. As curvas A/Ci foram realizadas nas três árvores, um galho por árvore e duas posições por galho, entre 8 e 12 horas. Aos cinco anos o Pinus caribaea var. hondurensis apresenta o dobro do volume de madeira do que o Pinus taeda. As duas avaliações fisiológicas mostraram valores similares entre tratamentos, para cada espécie. Os valores de Amax foram maiores durante o verão e o Pinus caribaea var. hondurensis mostrou grande sensibilidade, comparativamente ao Pinus taeda. Ao analisar os dados de A e gs ao longo do dia, observa-se também maiores variações do Pinus caribaea var. honduresis. Os valores médios de Amax para o verão e o inverno foram 8,2 e 4,8 ?mol m-2 s-1 e 6,8 e 6,3 ?mol m-2 s-1 para o Pinus caribaea var. hondurensis e o Pinus taeda, respectivamente. Ocorreu redução dos valores de A e gs com o aumento do DPV, para ambas as campanhas em relação ao Pinus caribaea var. hondurensis e somente no inverno para o Pinus taeda. As duas espécies apresentaram relação positiva entre fotossíntese e transpiração, sendo que o Pinus caribaea var. hondurensis apresenta maior eficiência no uso da água. As médias da AFE e nitrogênio foliar foram de 9,6 m²kg-1, 10,1g Kg-1 e 10,0 m²kg-1, 13,4g Kg-1, para o Pinus caribaea var. hondurensis e Pinus taeda, respectivamente. Em relação aos parâmetros fotossintéticos o Pinus taeda se destacou em ambas as campanhas, com valores médios de Vcmax e Jmax maiores que o Pinus caribaea var. hondurensis, relacionado à maiores concentrações de nitrogênio foliar. Não houve relação entre o crescimento em biomassa das árvores e as medições da fotossíntese a nível foliar, indicando que outros processos a nível de copa, uso e alocação de fotossintetizados devem ser investigados para explicar a diferença de crescimento. / The campaigns were conducted in trees with five years old of Pinus caribaea var. hondurensis and Pinus taeda in control plots (no fertilization and no irrigation) and fertilized and irrigated plots during summer and winter of 2012 to characterize the physiological variables: i) maximum photosynthetic capacity (Amax), ii) Photosynthesis throughout the day (A); iii) Changes in stomatal conductance (gs) in relation to the increase in vapor pressure deficit (VPD), and iv) Maximum rates of carboxilization (Vcmax) and maximum rates of electron transport (Jmax) based on A/Ci curves. The study was conducted in the project Potential Productivity of Pinus in Brazil, located at the Experimental Station of ESALQ/USP in Itatinga-SP. Three average trees per plot were chosen for physiological evaluations, performed with the LiCor 6400XT. The Amax measurement was performed in the middle third of the crown, in two branches per tree and two positions per branch, taken from 8 to 10am. To get the response of A and gs with increasing VPD, the measurements continued every hour, from 11 am to 3 pm. At the end of the measurements, the needles were collected for determination of specific leaf area (SLA) and leaf nitrogen (N). The A/Ci curves were performed in three trees, one branch per tree and two positions per branch were taken from 8 am to 12 pm. At five years, the Pinus caribaea var. hondurensis showed two-fold the wood volume of Pinus taeda. Both physiological measurements showed similar results between treatments for each species. Amax values were higher during summer, and Pinus caribaea var. hondurensis shower greater sensitivity compared to Pinus taeda. A and gs throughout the day showed higher variation in Pinus caribaea var. hondurensis. The average values of Amax for summer and winter were 8.2, 4.8 ?mol m-2 s-1 and 6.75, 6.3 ?mol m-2 s-1 for Pinus caribaea var. hondurensis and Pinus taeda, respectively. There was a reduction of A and gs with the increasing of DPV, for both campaigns for the Pinus caribaea var. hondurensis and only in winter campaign for Pinus taeda. Thus, the two species have different behaviors in response to climatic changes. The two species showed a positive relationship between photosynthesis and transpiration, with Pinus caribaea var. hondurensis showing greater water use efficiency. The average SLA and needle nitrogen were 9.6 m² kg-1, 10.1g kg-1 and 10 m² kg-1, 13.4g kg-1 for Pinus caribaea var. hondurensis and Pinus taeda, respectively. Photosynthetic parameters in Pinus taeda was higher in both campaigns, with average values of Vcmax and Jmax greater than in Pinus caribaea var. hondurensis, related to higher concentration of needle nitrogen. There was no relationship between tree biomass growth and leaf-level measurements of photosynthesis, indicating that other processes at crown level, use and allocation of photosynthates should be investigated to explain the difference in growth.

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.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The constant deficiency of available water resources and the society pressure for the rational water use in agriculture requires the correct management of the irrigation water. When a plant does not receive the right amount of water, it will affect the crop yield. The deficit irrigation contributes to increase the crops yield, comparing to a systems without irrigation, and as a results the agriculture will be more efficient preserving the quality ant quantity of natural recourses increasing or maintaining the crop yield. Therefore, this study is justified insofar as it seeks to identify deficit irrigation management in order to maintain satisfactory productivity, coupled with the water savings. The objective of this research was to evaluate water relations and gas exchange through the assessment of physiological variables that indicate changes in the crop yield of dry bean submitted to deficit irrigation. The experiment was conducted at the Federal University of Santa Maria, Brazil, under a mobile greenhouse, which was only closed during the occurrence of rain. In this way, there was no rainfall interference affecting the treatments. A completely randomized design was used with three replications. Treatments were consisted of four irrigation managements: 100% of accumulated crop evapotranspiration (ETc ac), and deficit irrigation of 75%, 50% and 25% of the ETc ac. Dry beans was sowed under a no tillage system, and the irrigation need was determined based on crop evapotranspiration values estimated using Penman-Monteith method, and the crop coefficients (Kc) used were those proposed by Allen et al. (1998). Irrigations were applied when the ETc accumulated a height of 20mm. The following leaf water relations and leaf gas exchanges were evaluated: Transpiration rate, stomatal conductance, leaf steam pressure deficit, internal concentration of CO2 and photosynthesis rate, using a LI-6400 (LI-Cor). With the values of photosynthesis rate, transpiration rate, stomatal conductance and internal concentration of CO2 were determined: transpiration instantaneous efficiency (photosynthesis rate/transpiration rate); intrinsic water use efficiency and (photosynthesis rate/stomatal conductance); carboxylation efficiency of the plants (photosynthesis rate/internal concentration of CO2). The following morphological features were evaluated: leaf area index, plant height and yield compounds (one hundred mass grains, number of seed plant and crop yield). The water use efficiency (EUA) was found by the ratio between grain yield (kg ha-1) and total depth applied (mm). During crop development accumulated ETc was 379,7 mm and was applied 122, 206, 290 and 376 mm of irrigation depth for the deficit irrigation treatment of 25%, 50%, 75% and 100% of ETc ac, respectively. The application of deficit irrigation reduced the leaf area index, plant height and reduction of 47,41% in the number of seed plant, 39,26%, in one hundred mass grain and 53,41% in crop yield. The reduction in water depth from 100% to 25% of ETc ac reduced by up to 91% of the stomatal concuctance and these plants had lower photosynthesis rate. The plants that received irrigation depth of 100% of ETc ac had higher E and carboxylation efficiency. The intrinsic water use efficiency and water use efficiency increased with the use of deficit irrigation. / A escassez dos recursos hídricos e a pressão social para o uso racional da água na agricultura exigem o correto uso e manejo da água de irrigação, pois, a falta ou excesso, comprometem o rendimento das culturas. O uso da irrigação, deficitária ou estratégica, contribui para o aumento da produtividade de grãos, comparando-se às condições de sequeiro, e resulta em uma agricultura economicamente mais eficiente, preservando os recursos naturais em termos de quantidade e qualidade, mantendo níveis satisfatórios de produtividade. Portanto, o presente estudo se justifica na medida em que se busca identificar manejos de irrigação deficitária que permitam manter níveis satisfatórios de produtividade, aliados à economia de água e energia. Assim, o objetivo desse trabalho foi avaliar as relações hídricas e as trocas gasosas, através da avaliação de variáveis fisiológicas que indiquem alterações na produção das plantas de feijão, quando submetidas a diferentes manejos de irrigação deficitária. O experimento foi desenvolvido na Universidade Federal de Santa Maria, Brasil, no interior de uma cobertura móvel, estruturada sobre trilhos metálicos, com movimentação mecânica, a qual somente foi fechada durante a ocorrência de chuvas. Dessa forma, não houve a interferência das chuvas durante a execução dos tratamentos. O delineamento experimental utilizado foi o inteiramente casualizado, com três repetições. Os tratamentos foram constituídos de quatro manejos de irrigação: reposição de 100% da evapotranspiração da cultura acumulada (ETc ac), e irrigação deficitária de 75%, 50% e 25% da ETc ac. A cultura do feijão foi semeada sob sistema de plantio direto e a necessidade de irrigação foi determinada com base na evapotranspiração da cultura, estimada pelo método de Penman-Monteith e os coeficientes de cultura (Kc) foram os propostos por Allen et al. (1998). Irrigações eram realizadas quando a ETc acumulava um valor de 20 mm. As seguintes relações hídricas e trocas gasosas das plantas foram avaliadas: taxa de transpiração, condutância estomática, déficit de pressão de vapor na folha, concentração interna de CO2 e taxa fotossintética, com o aparelho LI-6400 da Licor. Com os valores de taxa fotossintética, taxa de transpiração, condutância estomática e concentração interna de CO2 foram determinados: a eficiência instantânea da transpiração (razão taxa fotossintética/taxa de transpiração); a eficiência intrínseca do uso da água (razão taxa fotossintética/condutância estomática) e; a eficiência de carboxilação das plantas (razão taxa fotossintética/concentração interna de CO2). Foram avaliadas as seguintes características morfológicas nas plantas: índice de área foliar e altura de plantas e, os componentes de rendimento: massa de cem grãos, número de vagens por planta e rendimento de grãos. A eficiência de uso da água foi encontrada por meio da razão entre a produtividade de grãos (kg ha-1) e total de lâmina aplicada (mm). Durante o ciclo de desenvolvimento da cultura do feijão a ETc ac foi de 379,7 mm e foram aplicados 122, 206, 290 e 376 mm de lâmina de irrigação para os tratamentos de 25, 50, 75 e 100% da ETc ac, respectivamente. A aplicação da irrigação deficitária reduziu o índice de área foliar, a altura das plantas e causou reduções de até 47,41% no número de vagens por planta, 39,26%, na massa de cem grãos de feijão e 53,41% no rendimento de grãos. A redução da lâmina de irrigação de 100% para 25% da ETc ac reduziu em até 87% a condutância estomática das plantas e estas apresentaram menor taxa fotossintética. As plantas que receberam lâmina de irrigação de 100% da ETc ac apresentaram maiores taxa de transpiração e eficiência de carboxilação. A eficiência instrínseca do uso da água e a eficiência do uso da água aumentaram com a utilização da irrigação deficitária.

Stormwater bioretention cells (BRCs) are a variety of green stormwater infrastructure with the potential to restore pre-urban water balance, provided they can be tailored to infiltrate and evapotranspire (i.e., harvest) urban runoff in proportions consistent with pre-urban hydrologic conditions. This paper evaluates their capacity to do so, focusing on evapotranspirative harvest, which is relatively understudied, and the capacity of CSR (Competitve, Stress-tolerant, and Ruderal) functional type to serve as an overarching framework characterizing the water use strategy of BRC plants. The goal is to determine if harvest (and therefore the ratio of urban runoff infiltrated to harvested; the I:H ratio) might be fine-tuned to meet pre-urban values in BRCs through informed manipulation of plant community composition. This study focuses on 3 critical plant water use traits, the turgor loss point, the point of incipient water stress, and maximum stomatal conductance. A global plant traits meta-analysis identified degree of plant competitiveness and stress tolerance as significant determinants of all three water use traits, with stem type (woody vs herbaceous) also being significant, but only for turgor loss point. Based on these results, six water use scenarios appropriate for plants with different CSR type/stem type combinations were developed. BRC plants spanning the range of CSR types necessary to actionize these scenarios were determined to be available in eight major climate zones of the coterminous US, suggesting that regulating plant water use in BRCs using CSR is likely feasible. Hydraulic simulations (Hydrus 1D) were conducted for each scenario in all eight climate zones and revealed significant differences in evapotranspirative harvest and I:H ratios in simulated BRCs. Competitive woody plants had the highest evapotranspiration and lowest I:H ratios; 1.5-1.8 times more evapotranspiration and a 1.6-2 times lower I:H ratio than stress tolerant herbaceous plants, on average, across climate zones. Despite these significant differences, no simulated BRC in any climate zone was capable of reproducing pre-urban I:H ratios, regardless of plant type. More water was infiltrated than harvested in all scenarios and climates with the inverse being true for all pre-urban conditions. This suggests that absent additional sources of harvest (e.g., use of BRC water for nonpotable purposes such as toilet flushing and outdoor irrigation, or adoption of novel BRC designs that promote lateral exfiltration, stimulating "extra" evapotranspiration from nearby landscapes), BRCs will be unable to restore pre-urban water balance on their own. If true, then using BRCs in combination with other green technologies (particularly those biased towards harvest), may be the best path forward for balancing urban water budgets. / Master of Science / Stormwater bioretention cells (BRCs) are a variety of green infrastructure designed to manage urban stormwater flows that can dramatically reduce the amount of stormwater that is rapidly (and unnaturally) conveyed from paved surfaces to ecosystems. Their ability to recreate natural flow conditions is dependent on them balancing rates of infiltration – slowly filtering water down to the water table – and evapotranspiration – letting plants capture and transpire water. This paper evaluates the extent to which different plant functional types (competitive, stress tolerant, and ruderal (weedy)) can be used to regulate this balance, bringing urban hydrologic conditions closer to pre-urban ones. Competitiveness and stress tolerance were found to significantly influence plant water use traits, as was plant stem type (woody vs herbaceous) to a lesser extent (i.e., managing water budgets using CSR functional type is theoretically possible). Published BRC vegetation guidelines in 8 major US climate zones were found to include both competitive and stress tolerant species (i.e., the range of functional types required to regulate BRC water balance exists, suggesting it is feasible). Finally, hydraulic simulations conducted under six plant water use scenarios (reflecting different CSR types and stem types) revealed significant differences in the ratio of water infiltrated to evapotranspired by BRCs (i.e., changing plant functional types can meaningfully influence BRC water balance). This said, the magnitude of this effect may be insufficient to return urban catchments to a pre-urban state. All BRCs infiltrated too much water in our simulations suggesting that absent additional sources of harvest (for instance., use of BRC water for nonpotable purposes such as toilet flushing or outdoor irrigation), BRCs will be unable to restore pre-urban water balance on their own. If true, then using BRCs in combination with other green technologies (particularly those biased towards harvest), may be the best path forward for balancing urban water budgets.

Master of Science / Department of Agronomy / Robert M. Aiken / Mary B. Kirkham / Transpiration efficiency (TE) is defined as total biomass produced per unit of water transpired. Improvement of TE means maximizing crop production per unit of water used. The objectives of the study were to examine, at the leaf level and the whole plant level, the variation in TE for sorghum [Sorghum bicolor (L.) Moench] accessions, previously screened for TE and to test physiological mechanisms that may account for differences in TE. Three field studies and two mini-lysimeter studies (one done in pots under greenhouse conditions and one done in pots in the field) were conducted with eight accessions. Instantaneous measurements of assimilation (A), stomatal conductance (gs), and transpiration by gas exchange provided measures of the transpiration efficiency at the leaf level. Growth observations and soil water balance in field plots quantified components of whole-plant TE. Growth and development measurements showed significant difference, explaining the existence of photoperiod sensitivity among the sorghum genotypes. Assimilation (A), stomatal conductance (gs), and maximum quantum efficiency of photosystem II (Fv/Fm) were consistently greater for accession PI533946 (from India) and greater for accession PI295121 (from Australia) in both field and the field-pot studies (p<0.05). Internal carbon dioxide (Ci), an indicator of intrinsic transpiration efficiency, differed among lines under field conditions (p<0.05). Leaf relative water content (RWC), measured in the greenhouse, and did not differ among the eight accessions. No consistent differences in biomass and water use were detected among lines under field conditions. In conclusion, developing reliable selection indices for TE will require a greater understanding of whole-plant physiological processes to utilize the differences in TE observed at the leaf level.

Baby spinach is a relatively new crop in South Africa with both commercial significance and reputed health benefits. It is known to assist in combating degenerative conditions associated with ageing, such as heart disease, cardiovascular disease, Alzheimer’s disease, cataracts and several forms of cancer. Three parallel NPK trials were conducted to investigate the effects of nitrogen (N), phosphorus (P) and potassium (K) on the growth and development of baby spinach. N and P treatments were arranged as (0, 45, 75, 105, 120 kg.ha -1 N and P), and K treatments were arranged as (0, 63, 85, 127, 148 kg.ha -1) in a randomised complete block designed with four replicates. Results showed that yield, dry matter, chlorophyll content and Leaf Area Index (LAI) were significantly increased by increasing the N application, while K had a significant effect on the LAI but not on yield, dry matter, chlorophyll content or stomatal conductance. Nitrogen treatments quadrupled fresh yield, dry matter and chlorophyll content, reaching maximum impact at 75 kg.ha-1 N. Phosphorus application showed significantly increased yields, dry matter and chlorophyll content, reaching maximum impact at 75 kg.ha-1 P. Therefore, to achieve optimum growth with N and P, 75 kg.ha-1 is recommended. The optimum rates of N, P and K were then used to formulate a NPK combined trial which was arranged as 0, 30:30:40, 45:45:60, 60:60:70, 75:75:90 kg.ha-1 in a randomised complete block design with three replicates. The results showed that maximum impact on yield, chlorophyll content, fresh and dry matter was achieved when combined NPK was applied at 45:45:60 / Agriculture and  Animal Health / M. Sc. (Agriculture)

La zone sahélienne a connu une baisse des précipitations et d’importants changements d'utilisation des terres ces dernières décennies qui ont conduit à une forte régression du couvert ligneux. Pourtant, Guiera senegalesis J.F. Gmel est une Combretaceae semi-sempervirente, dont la dominance s'est accrue avec la pression agricole dans la bande soudano-sahélienne où elle joue un rôle socio-économique et agroforestier important. Elle constitue donc un bon modèle pour étudier les réponses hydriques du couvert ligneux actuel à la sécheresse et les modifications de ces réponses sous l'effet de la coupe.Les objectifs de ce travail de thèse étaient : 1) de caractériser et quantifier les processus de régulation hydrique chez G. senegalensis et de déterminer ses limites fonctionnelles, afin d’estimer sa marge de sécurité dans ses conditions actuelles de croissance, 2) d’estimer l’effet de la coupe annuelle sur ses processus de régulation et 3) d’analyser les variations de ses traits foliaires en fonction de la saison et des conditions de croissance.Les mesures et les observations ont été réalisées d’avril 2009 à février 2011 sur une jachère âgée, sur une jeune jachère et sur deux champs de mil adjacents aux deux jachères respectivement. A l'échelle de l'arbuste, le potentiel hydrique foliaire et la conductance stomatique ont été mesurés au cours de ces deux saisons de croissance sur un échantillon d'arbustes dans les trois types de couvert. Le taux de transpiration foliaire et la conductance hydraulique sol-feuille en ont été déduits. A l’échelle du rameau, ont été suivi la dynamique du nombre de feuilles, de la surface moyenne des feuilles, du diamètre moyen des tiges qui les portent. La durée de vie moyenne des feuilles et leur masse surfacique ont été mesurées. La courbe de vulnérabilité à la cavitation de l'espèce, qui est la perte de la conductivité hydraulique en fonction du potentiel hydrique, a été réalisée à partir de plusieurs segments de branches passés au CAVITRON en laboratoire.Les principaux résultats obtenus sont que la fermeture des stomates qui permet à l’espèce de réguler ses pertes en eau a lieu à un niveau faible de cavitation du xylème (30%). Ainsi, l’espèce peut survivre dans les conditions sahéliennes grâce à une « marge de sécurité » positive de +0,6 MPa. La régulation stomatique couplée à un ajustement foliaire permet à l’espèce de maintenir son équilibre hydrique au cours de la saison sèche chez les arbustes matures non perturbés. La baisse des potentiels hydriques foliaires de base et minimum en réponse à la sécheresse saisonnière est isohydrodynamique et est plus élevé chez les arbustes matures, suggérant que les repousses de l'année sont moins stressées. De plus, la coupe a pour effet de découpler l’ajustement foliaire de la régulation stomatique et entraîne une production de feuilles et une croissance des jeunes rameaux continues tout au long de l'année chez les repousses, grâce à une conductance hydraulique sol-feuille deux fois plus élevée que chez les arbustes matures. Enfin, la durée de vie des feuilles s’allonge avec l’âge des rameaux d'une année comme avec l'âge du peuplement, tandis que la masse surfacique foliaire augmente progressivement de la même façon quand on passe de la saison des pluies à la saison sèche, quel que soit l'âge du peuplement.Ces traits fonctionnels contribuent à ce que l’espèce puisse à la fois résister aux conditions de sécheresse dans lesquelles elle croît et ré-allouer de façon intense des ressources, stockées probablement dans les racines, à la reconstruction rapide de sa partie aérienne à la suite d'une coupe. Les limites d'une telle stratégie restent cependant à identifier, en particulier le seuil d'épuisement des ressources sous l'effet de la répétition annuelle des coupes. / Sahel suffered from severe rainfall decreases combined to great changes in land use during the last decades that led to strong decrease in the woody cover. However, Guiera senegalesis J.F. Gmel is a semi-evergreen Combretaceae whose dominance rose with crop pressure in the Sudano-Sahelian band where it plays an important socio-economic role through agroforestry. Consequently, this is a good model to study hydric responses of the present woody cover to drought and the effect of cutting on these responses.The aims of this work were: 1) to characterize and quantify hydric regulation processes in G. senegalesis and to determine its specific functional limits, in order to estimate its safety margin in its current growth conditions, 2) to estimate cut effect on these processes and 3) to analyze variations of its leaf traits according to the season and its specific growth conditions.Measurements and observations were conducted from April 2009 to February 2011 on an old fallow, on a young fallow, and on the two crop fields adjacent to the two fallows respectively. At the shrub scale, leaf water potential and stomatal conductance were measured during the two growing seasons on shrub samples in the three cover type. The leaf transpiration rate and the soil-to-leaf conductivity were deduced. At the stem scale, the dynamics of the number of leaves, the mean leaf area (LMA), the mean diameter of the stems that carry them, the mean leaf life span, and the leaf mass per area were monitored. The species vulnerability curve to cavitation, which is the loss of conductivity as a function of the water potential, was obtained from several peaces of branches treated in a CAVITRON at the laboratory.The main results obtained were that the stomatal closure that allows species to regulate its water loss occurs at a low rate of xylem cavitation (30%). Thus, the species can survive in its Sahelian conditions thanks to a positive “safety margin” of +0.6 MPa. Stomatal regulation coupled with leaf adjustment allows the species to maintain its water balance during the dry season in mature and undisturbed shrubs. The decrease in predawn and midday leaf water potentials in response to seasonal drought was isohydrodynamic, and it was greater in mature shrubs, suggesting that current year resprouts are under less stress. In addition, cutting decouple leaf adjustment from stomatal regulation, leading to continuous leaf production and young stem growth all over the year, thanks to a soil-to-leaf conductivity seven times higher in the current year's resprouts than in the mature shrubs. Finally, leaf life span increases with the current year's stem age as well as with the stand age, while the LMA progressively increases from the rainy season to the dry season, similarly whatever the stand age.These functional traits contribute to the species resistance to the drought conditions under which it grows, but also, following the cutting, to intensively re-allocate resources, probably from the root reserve, to the fast re-building of the aerial part. However, the limits of such a strategy remain to be identified, especially the resource exhaustion threshold under repetitive yearly cutting.

As relações hídricas e fisiológicas em plantas de lima ácida ‘Tahiti’ sob estresse hídrico foram estudadas tendo-se como principais objetivos: (a) verificar a sazonalidade da evapotranspiração e o coeficiente de cultivo com o uso de lisímetro de pesagem baseado em célula de carga eletrônica, (b) determinar o limite crítico da água disponível em função da evapotranspiração, trocas gasosas e potencial de água na folha durante um período de estresse hídrico e (c) avaliar o efeito da supressão da irrigação durante diferentes períodos fenológicos sobre o desenvolvimento vegetativo, na produtividade e qualidade do fruto. Este experimento foi conduzido na Fazenda Areão do Departamento de Engenharia Rural da ESALQ/USP, em Piracicaba, SP, em um pomar de 1 hectare no espaçamento de 7 X 4 m com lima ácida ‘Tahiti’ (Citrus latifolia Tanaka) enxertadas em citrumelo ‘Swingle’ [Poncirus trifoliata (L.) Raf. x C. paradisi Macf.] irrigadas por gotejamento. Para as medidas fisiológicas, foram utilizados equipamentos portáteis como a câmara de pressão e analisador de gases por infravermelho além de medidas do desenvolvimento vegetativo e produtivo. O monitoramento da água solo foi realizado por tensiômetros e sondas de TDR. A Evapotranspiração de Referência foi obtida com uma estação agrometeorológica automatizada presente na área. Verificou-se um efeito sazonal na evapotranspiração, com uma redução superior a 50% no período verãoinverno, possibilitando a economia da irrigação no período. A evapotranspiração, trocas gasosas e potencial da água na folha ao amanhecer foram diminuídos pelo esgotamento de 40% da água disponível do solo por ocasião do final do período de inverno. A supressão da irrigação no período de Setembro a Março diminuiu o potencial matricial do solo e promoveu um estresse leve nas plantas não-irrigadas, não se observando efeitos negativos no desenvolvimento vegetativo, produtivo e na qualidade dos frutos formados. Recomenda-se o potencial da água no folha ao amanhecer para manejo da irrigação, mantendo-o maior que -0,6 MPa, para evitar o estresse hídrico em plantas de limeira ácida ‘Tahiti’. / Water and physiologic relations in acid lime trees under water stress were studied with the following purposes: (a) to verify the seasonal effect of evapotranspiration and the crop coefficient in non-stressed trees by weighing lysimeter; (b) to determine the critical soil water depletion for evapotranspiration, gas exchange as well as the leaf water potential during a stage of growing of the trees and (c) to determine the effect of the irrigation suppression on growth, yield and fruit quality during different phenological periods. The experiment was carried out an experimental farm at College of Agriculture Luiz de Queiroz (ESALQ), in Piracicaba and performed from 2003 to 2005 in a 1 hectare orchard planted with ‘Tahiti’ (Citrus latifolia Tanaka) grafted on ‘Swingle’ [Poncirus trifoliata (L.) Raf. x C. paradisi Macf. ] rootstock. The trees were spaced 7 x 4 m apart and drip-irrigated. For physiologic measurements were used portable equipments such as a pressure chamber and an infrared gas analyzer as well measurements of vegetative and productive growth. The soil water status was monitored by tensiometers and TDR probes. The reference evapotranspiration was obtained by an automatic weather station presented on the area. There was a seasonal effect on evapotranspiration with a reduction higher than 50% forward to summer-winter, being able to water savings in the period. The evapotranspiration, gas exchange and leaf water potential at predawn were decreased when the soil water available was depleted by 40% in the end of winter. The irrigation suppression from September and March decreased the soil matric potential and promoted a light stress level in non-irrigated trees, but without negative effects on vegetative, productive and fruit quality. We recommend the leaf water potential at predawn for irrigation scheduling, keeping higher than -0.6 MPa for avoid water stress in acid lime trees.