O objetivo deste trabalho foi avaliar a atividade das enzimas redutase do nitrato (RN) e glutamina sintetase (GS) em mudas de Coffea arabica L cv Obatã IAC 1669-20 em função dos atributos ecofisiológicos. O experimento foi conduzido em casa de vegetação no Laboratório de Biotecnologia Agrícola do Departamento de Ciências Biológicas da Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo. Para a realização do experimento adotou-se o delineamento inteiramente casualizado com dois tratamentos: T1 (100% de luz) e T2 (50% de luz) e cinco repetições. As determinações das atividades enzimáticas foram feitas às 07:00 h; 12:00 h; 17:00 h e 22:00 h, bem como dos atributos ecofisiológicos: temperatura atmosférica; temperatura foliar; radiação fotossinteticamente ativa; condutância estomática; taxa de fotossíntese líquida; taxa de transpiração e proteína total solúvel. O nível de exposição à luminosidade altera a atividade da redutase do nitrato (RN), cujo valor foi menor nas plantas a pleno sol às 12:00 h e 17:00 h. A saturação lumínica e a maior temperatura foliar em relação ao ambiente, às 12:00 h, diminuiu as trocas gasosas (CO2 e vapor d’água) e a atividade da RN. Ao longo do período luminoso, independentemente do nível de exposição à luminosidade, decresceu a atividade da glutamina sintetase (GS). A disponibilidade de amônio proveniente da ação da RN no período noturno elevou a atividade da GS, enquanto a fotorrespiração, por hipótese, forneceu o substrato (NH4 +) para a atividade dessa enzima (GS) nas plantas a pleno sol ao meio dia. A inibição da redutase do nitrato (RN) no cafeeiro proporcionada pela fotorrespiração se dá, por hipótese, em resposta a produção de glutamina por meio da atividade da glutamina sintetase (GS). / The aim of this work was to evaluate the activity of the enzymes nitrate reductase (RN) and glutamine synthetase (GS) in seedlings of Coffea arabica L cv Obatã IAC 1669 - 20 in face of the eco-physiological attributes. The experiment was conducted in a greenhouse at the Laboratory of Agricultural Biotechnology in the Biological Science Department of the Superior School of Agriculture "Luiz de Queiroz", São Paulo University. The completely randomized experimental design was utilized for the experiment with two treatments: T1 (100% of light) e T2 (50% of light), each on made up of five replicates. The enzymatic activities and eco-physiological attributes determinations such as air temperature, leaf temperature, photosynthetically active radiation, stomatal conductance, net photosynthesis rate, transpiration rate and total soluble protein were made at 7:00 AM, 12:00 AM, 5:00 PM and 10:00 PM. The level of radiation exposition changes the nitrate reductase activity, whose value was smaller in plants at full sun at 12:00 AM and 5:00 PM. The light saturation and the higher leaf temperature in relation to the environment, at 12:00 AM, reduced the gas exchanges (CO2 and water vapor) and RN activity. Along the light period, independently of radiation exposition level, the activity of the glutamine synthetase decreased. The availability of ammonium provided by RN during dark period, independently of the treatments, increase the GS activity, while photorespiration, hypothetically, supplied the substrate (NH4+) to the GS action in plants under full sun at 12:00 AM. The RN inhibition in coffee plants provides the photorespiration occurred in response to the glutamine production through the GS activity.

Submitted by (ana.araujo@ufrpe.br) on 2017-02-17T12:38:37Z No. of bitstreams: 1 Jacqueline Wanessa de Lima Pereira.pdf: 684135 bytes, checksum: dc0f8da93d2685268558a2dc803e4044 (MD5) / Made available in DSpace on 2017-02-17T12:38:37Z (GMT). No. of bitstreams: 1 Jacqueline Wanessa de Lima Pereira.pdf: 684135 bytes, checksum: dc0f8da93d2685268558a2dc803e4044 (MD5) Previous issue date: 2010-07-07 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Peanut is one of the most cultivated oily in the world. For countries of semi-arid climate, as Brazil, for example, the peanut is an important alternative to farming due to the low water requirement during the cycle and adaptation to environments of high temperature and solar radiation. Despite the tolerance to low water availability, peanuts’ requirements are not the same over the cycle. Water shortage during the reproductive phase directly affects the formation and filling of pods, even in cultivars notoriously resistant to water deficit. According to some authors, which makes the peanut plant tolerant to environmental adversities are the morphological and physiological mechanisms that maintain the plant turgidity, even under low water availability conditions. Among those are cited changes in water ratios (stomatal behavior and osmotic adjustment) and the expansion of the root system for deeper and wetter soil areas. Faced with this adaptability, understanding the role of water deficit during the production cycle of culture is essential for adopting management strategies that enable secure production in areas prone to drought. In this work, four peanut genotypes of different growth habits were subjected to 21 days of water stress in a greenhouse. The planting was performed in pots containing sandy-loam texture soil, previously limed and fertilized. The experimental design was randomized with a bi-factorial 4x2 scheme (4 genotypes x 2 water treatments) with 10 repetitions. the water treatment were control (daily irrigation) and stress (irrigation suspension). The variables evaluated were difusive resistance, transpiration, leaf water potential, relative water content, proline content, chlorophyll content, root length, dry weight of pods, harvest index and stress tolerance index (STI). Under stress conditions, stomatal behavior was changed from the second week, when all genotypes significantly increased abaxial surface diffusive resistance and reduced sweating, highlighting the isoline LBM Branco Moita/08. The water potential of all genotypes was significantly reduced, being more expressive in isolines LBM-Branco Moita/08 and LBR-Branco Rasteiro/08 reaching more negative values. The LBM-Branco Moita/08 also had higher levels of proline and along with a BR 1 had the greatest expansion of the root system as adaptive way. In the production aspect, the LBM-Branco Moita/08 revealed the lowest reductions in weight of pods and harvest index when subjected to water deficit. Regarding the STI, values obtained with the cv. BR1 confirm its suitability for management in semi-arid environments; the strains LBR-Branco Rasteiro/08 and LBM-Branco Moita/08 also showed significant production performance in environments with water restriction. / O amendoim é uma das oleaginosas mais cultivadas no mundo. Para os países de clima semi-árido, o Brasil, por exemplo, o amendoim é uma importante alternativa para a agricultura devido à baixa exigência hídrica durante o ciclo e adaptação aos ambientes com altas temperaturas e radiação solar. Apesar da tolerância à baixa disponibilidade hídrica, as exigências do amendoim não são as mesmas ao longo do ciclo. A escassez de água durante a fase reprodutiva afeta diretamente a formação e o enchimento das vagens, mesmo em cultivares notoriamente resistentes ao déficit hídrico. Segundo alguns autores, o que torna a planta do amendoim tolerante às adversidades ambientais são os mecanismos morfológicos e fisiológicos que mantêm a turgescência das plantas, mesmo sob condições de baixa disponibilidade de água. Entre as mudanças já estão em relações hídricas (comportamento estomático e ajustamento osmótico) e a expansão do sistema radicular para as áreas mais profundas e úmidas do solo. Confrontados com esta capacidade de adaptação, a compreensão do papel do déficit hídrico durante o ciclo produtivo da cultura é essencial para a adoção de estratégias de manejo que permitam uma produção segura em áreas propensas à seca. Neste trabalho, quatro genótipos de amendoim de diferentes hábitos de crescimento foram submetidos a 21 dias de estresse hídrico em casa de vegetação. O plantio foi realizado em vasos contendo solo de textura franco-arenosa, previamente corrigido e adubado. O delineamento experimental foi inteiramente casualizado, com um esquema bi-fatorial 4x2 (4 genótipos x 2 tratamentos de água), com 10 repetições. Os tratamentos hídricos foram: controle (rega diária) e estresse (suspensão de rega). As variáveis avaliadas foram: resistência difusiva, transpiração, potencial hídrico, teor relativo de água, teor de prolina, teor de clorofila, comprimento radicular, peso seco das vagens, índice de colheita e índice de tolerância ao stress (STI). Sob condições de estresse, comportamento estomático foi alterado a partir da segunda semana, quando todos os genótipos aumentaram significativamente a resistência difusiva da superfície abaxial e reduziram a transpiração, destacando a isolinha LBM-Branco Moita/08. O potencial de água de todos os genótipos foi significativamente reduzido, sendo mais expressivos em isolinhas LBM-Branco Moita/08 e LBR-Branco Rasteiro/08 atingindo valores mais negativos. A LBM-Branco Moita/08 também apresentou elevado acúmulo de prolina e, juntamente com um BR 1 teve a maior expansão do sistema radicular como forma de adaptação. No aspecto de produção, a LBM-Branco Moita/08 revelou as menores reduções no peso das vagens e índice de colheita, quando submetida ao déficit hídrico. Quanto ao STI, os valores obtidos com a cv. BR1 confirmar a sua aptidão para o manejo em ambientes semi-árido, as isolinhas LBR-Branco Rasteiro/08 e LBM-Branco Moita/08 também apresentaram desempenho significativo de produção em ambientes com restrição hídrica.

O uso crescente de irrigação na cafeicultura devido ao cultivo em áreas com maior deficiência hídrica exige conhecimento sobre o consumo de água da cultura. Para contribuir para esse conhecimento, a evapotranspiração global do cafezal (ETc) e sua partição nos fluxos componentes evapotranspiração das linhas de cafeeiros (ETlin), evapotranspiração das entrelinhas (ETel) e a transpiração dos cafeeiros (T) foram determinadas em um cafezal de Coffea arabica cv. Obatã IAC-1669-20, cultivado em Piracicaba, SP, em espaçamento de 3,50 m x 0,90 m, irrigado por gotejamento e idade entre 3 a 4 anos, com medidas de setembro/04 a maio/05 e em setembro e outubro de 2005. ETc foi determinada pelo método de balanço de energia-razão de Bowen, ETlin por lisímetros de células de carga, sendo estes usados em vários períodos com o solo coberto com plástico para determinação direta da transpiração e para calibrar o método da sonda de dissipação térmica, usado na determinação do fluxo de seiva (FS) dos cafeeiros. Em abril-maio/05, FS foi usado como uma estimativa de T diária. ETc e componentes foram relacionados com a evapotranspiração de referência estimada pelos métodos de Penman- Monteith (ETo 1) e do tanque classe A (ETo 2). O calor latente de vaporização (LE) representou a maior fração na partição da energia disponível (saldo de radiação menos fluxo de calor no solo), com variação de 73 a 80 % ao longo dos meses, não se podendo descartar a contribuição de calor advectivo para os valores encontrados nos meses secos. ETc cresceu a partir de setembro/04 a fevereiro/05 (2,75 a 4,58 mm d-1), refletindo principalmente o incremento de área foliar e diminuindo, posteriormente, até maio/05 (3,13 mm d-1) com a diminuição da demanda atmosférica. Em setembro-outubro/05 os valores foram maiores (2,93 e 4,29 mm d-1) do que os observados no mesmo período em 2004, sendo o aumento da área foliar uma das responsáveis pelo fato. A relação ETc/ETo (“Kc global da cultura”) foi maior quando calculada com ETo 1 do que com ETo 2, sendo os valores crescentes até janeiro/05 (1,20 com ETo 1 e 1,21 com ETo 2) mas com o menor valor em setembro/04 (0,67 e 0,54) e com diminuição da tendência de acréscimo em fevereiro/05 (1,17 e 0,73), provavelmente pela regulação estomática dos cafeeiros devido à alta demanda atmosférica nesses meses. A contribuição de ETlin para a ETc variou pouco entre setembro/04 e fevereiro/05 (24 % a 31 %), aumentando em março e abril (35 % e 40 %), valores esses próximos da proporção entre a área de solo coberta pelos cafeeiros e a área total (linhas+entrelinhas). A relação ETlin/ETo variou entre 0,20 (uso de ETo 1) e 0,16 (com ETo 2) em setembro/04 a 0,36-0,47 (com ETo 1) e 0,25-0,49 nos outros meses. A T dos cafeeiros por unidade de área foliar diminuiu com o aumento da área foliar. A relação T/ETlin variou de 72 % em fevereiro a 46 % em abril, sendo o valor de T/ETo (“Kc basal”) variável entre 0,13 (com ETo 1) e 0,10 (com ETo 2) em setembro a 0,30 (independente do método de estimativa de ETo) em abril e maio/04, provavelmente refletindo a menor atividade fisiológica. / The increasing use of irrigation in coffee plantations in Brazil, due to the deplacement of the crop to areas where water deficit occurs, requires knowledge about crop water consumption. Aiming to know more about coffee plantation water consumption, daily crop evapotranspiration (ETc) and its partition in row evapotranspiration (ETrow), interrows evapotanspiration (ETint) and coffee plants transpiration (T) were determined in a drip-irrigated coffee plantation (cv. Obatã IAC-1669-20), cultivated at 3.5 m between rows and 0.9m between plants, in Piracicaba, São Paulo State, Brazil. The ET and wheater variables measurements were carried out from September 2004 to May 2005 and from September to October 2005. ETc was determined by he Bowen ratio-energy balance method, ETrow by load cell lysimeters and T with lysimeters with soil surface covered with plastic or by sap flow determined with the thermal dissipation probe method (TDP). Lysimeters were also used to calibrate the TDP method. So, sap flow was adopted as representative of coffee plants transpiration for 24-h period. ET and its components were related to the reference evapotranspiration, determined by Penman-Monteith (ETo 1) and Class-A pan (ETo 2) methods. Latent heat of vaporization (LE) represented the major fraction (73 a 80 %) of the available energy (net radiation less soil heat flux) along the months, but a contribution of advective heat flux in dry months must be considered for the observed values. ETc increased from September 2004 to February 2005 (from 2.75 to 4.58 mm d-1), which is reflecting the increase of coffee plants leaf area. From March to May 2005, ETc decreased according to the decrease of the atmospheric demand. In September and October 2005, ETc were greater, respectively, 2.93 and 4.29 mm d-1, than those observed in the same months of 2004 and, again the increase of leaf area was the responsable for these differences. ETc/ETo, defined as a “global Kc”, was greater when determined with ETo 1 than when determined with ETo 2, increasing with the leaf area.from September 2004 (0.67 with ETo 1 and 0.54 with ETo 2) to January 2005 (1,20 and 1,21). In February Kc decreased to 1.17 (with ETo 1) and 0.73 (with ETo 2), probably as a consequence of the coffee plants stomatal control due to the high atmospheric demand. The contribution of ETrow to ETc varied between 25 % and 31 % for the period September 2004- February 2005, increasing in March and April 2005 (35 % and 40 %). These values were close to those observed for the ratio between the area of soil covered by coffee plants and the total area (rows+interrows). ETlin/ETo changed from 0.20 or 0.16 (using ETo 1 and ETo 2, respectively) in September 2004 to 0.36-0.47 (with ETo 1) or 0.25- 0.49 (with ETo 2) in the other months. Coffee plant transpiration per leaf area unit decresead with the increase of leaf area. T/ETrow changed from 0.72 (February) to 0.46 (April). T/ETo (“basal Kc”) ranged from 0.13 (with ETo 1) or 0.10 (with ETo 2) in September 2004 to 0.30 (for both ETo 1 or ETo 2) in February, but decreased in April and May 2005, probably reflecting the decrease in the physiological activity of coffee plants.

Native plant communities and agricultural land are commonly converted to urban areas as cities across the Western United States continue to grow and expand. This expansion is typically accompanied by afforestation where a common goal among communities is to maximize shade tree composition. Planted forests in these regions are commonly composed of introduced tree species native to mesic environments and their ability to persist is dependent on consistent irrigation inputs. Many potential ecosystem services may be derived from planting trees in urban and suburban areas; however, there are also costs associated with extensive afforestation, and shade tree cover may have significant implications on municipal water budgets. In this study I evaluate variation in daily and seasonal water use of regionally common suburban landscape tree species in the Heber Valley (Wasatch County, Utah). I had two primary objectives: (1) to identify and understand the differences in transpiration between landscape tree species in a suburban setting and (2) to assess the sensitivity of sap flux and transpiration to variation in vapor pressure deficit, wind speed, and incoming shortwave radiation. I used Granier's thermal dissipation method to measure the temperature difference (ΔT) between two sap flux probes. The empirical equation developed by Granier was used to convert ΔT into sap flux density (Jo) measurements, which were then scaled to whole-tree transpiration. There were consistent and substantial differences in sap flux between tree species. I found that Picea pungens under irrigated growing conditions, on average, had Jo rates that were 32% greater and whole tree water use (ET) rates that were 550% greater than all other species studied. The findings of Jo may be partially explained by xylem architecture and physiological control over stomatal aperture. However, the rate of water flux in the outermost portion of sapwood does not necessarily determine the magnitude of whole tree transpiration. Rather, ET in this study was largely explained by the combined effects of irrigation, tree size, and sapwood to heartwood ratio.

During the period of October 1974 to August 1976, a study was conducted to measure the effects of surface soil removal on plant production, plant transpiration rates, nitrate nitrogen mineralization rates, and selected hydrologic parameters (infiltration rates, potential sediment production, and chemical quality of runoff water). The treatments were incremental 7.6 centimeter soil layers to a depth of 30.5 centimeters. Plant production and transpiration ratios (or water use efficiencies) were measured in greenhouse studies using Agrogyron desertorum grown in the incremental 7.6 centimeter soil layers from five study sites throughout the state of Utah, (Blanding, Brush Creek, Milford, Huntington, and Dove Creek). Significant decreases in plant production and increases in transpiration ratios were measured for all sites at incremental depths beyond 7.6 centimeters. These changes in plant production and transpiration ratios were found to be linearly related to the nitrate nitrogen content of the soils as determined at the time the soils were collected for use in the greenhouse. Nitrogen mineralization rates for a 6 week period were measured under field conditions at Milford and Blanding for each of the 7.6 centimeter incremental soil layers. Nitrate nitrogen mineralization was linearly correlated to the organic carbon content of the soil. Decreased mineralization rates as measured in the field at both study sites were reflected in significant increases in plant water requirements and also decreases in production as measured in greenhouse studies. Hydrologic parameters were measured at each 7.6 centimeter incremental soil depth using a Rocky Mountain infiltrometer. With one exception, significant differences in infiltration capacities among treatment depths did not occur during either 1975 or 1976 at either the Blanding or Milford site. At the Blanding site a significant decrease in the infiltration capacity occurred beyond the 22.9 centimeter depth due to a hardpan development. A significant change in infiltration capacities was noted between the 1975 and 1976 field seasons as pooled over both treatment depths and study sites. There were no significant differences in potential sediment production between sites or among treatment depths within a site. In terms of runoff water quality, a significant change in phosphorus was observed only at the Blanding site between the 1975 and 1976 field seasons. Significant differences in potassium concentrations were found to exist between sites and among soil depths.

Au delà de la diversité architecturale bien décrite entre variétés chez le pommier, une variabilité fonctionnelle est suspectée, encore très mal connue, qui pourrait se répercuter sur leur productivité et sur leurs capacités d'adaptation. Par ailleurs, il est postulé que la variabilité fonctionnelle des cultivars à une échelle intégrée dépend à la fois de l'organisation architecturale de leur système aérien et d'une variabilité du fonctionnement de leur feuillage.<br />La comparaison qui a été réalisée entre génotypes a porté sur 4 cultivars de pommier : Fuji et Braeburn d'une part, Ariane et X3305 d'autre part, dont les arbres étaient respectivement âgés de sept ans et de deux ans au début de l'étude. Les arbres ont été cultivés dans un verger expérimental irrigué et soumis à des pratiques culturales standard.<br />L'étude de la variabilité architecturale entre arbres a mis en évidence des différences de dynamique de mise en place de la surface foliaire entre individus jeunes et plus âgés. Des différences de composition raméale entre arbres de même âge ont également été révélées, ayant pour conséquence des différences d'efficience d'interception lumineuse entre cultivars qui ont été quantifiées par le paramètre STAR (Silhouette to Total leaf Area Ratio). Une méthode de description de la structure des arbres en 3D, reposant sur une approche mixte de digitalisation et de reconstruction du feuillage, a été validée.<br />L'étude fonctionnelle à l'échelle foliaire a mis en évidence une diversité de la régulation stomatique des 4 génotypes en réponse aux facteurs abiotiques (modèle de Jarvis), alors que les paramètres photosynthétiques (modèle biochimique de Farquhar) s'avéraient peu variables.<br />Les caractéristiques architecturales et fonctionnelles de chaque cultivars ont été prises en compte dans la paramétrisation et l'utilisation du modèle structure-fonction RATP, afin d'évaluer l'impact de leur couplage sur les capacités d'interception lumineuse, de transpiration et d'assimilation de carbone à l'échelle intégrée de la branche fruitière. Une analyse de sensibilité du modèle pour le cultivar Braeburn a permis de mettre en évidence le rôle prépondérant de l'architecture des arbres dans la variabilité de fonctionnement à cette échelle.<br />Les perspectives ouvertes par cette approche écophysiologique chez le pommier au moyen d'un modèle structure fonction sont discutées.

Les variations de transpiration totale sous contraintes hydriques, à la fois atmosphérique et édaphique, sont étudiées pour des arbres matures d'Hevea brasiliensis (clone RRIM600) dans une zone limitée en eau du Nord-Est de la Thaïlande. Les variations sont analysées et comparées entre une sécheresse transitoire en saison des pluies et la sécheresse saisonnière caractérisée par des fluctuations de la surface foliaire (sénescence foliaire, chute des feuilles and re-feuillaison) et de la croissance racinaire en profondeur. Les réponses physiologiques sont analysées dans le cadre d'un modèle hydraulique simple appelé "RER_ET0". Ce modèle est principalement basé sur une valeur critique du potentiel hydrique foliaire (ψcrit) et sur les réponses, de la conductivité hydraulique totale de l'arbre (gL) et du potentiel hydrique de base (ψpredawn), à la disponibilité en eau du sol (REW). Une estimation précise et en continue de la transpiration totale des arbres durant une année complète était une mesure clé de cette étude avec des mesures concomitantes des conditions environnementales et du potentiel hydrique foliaire (ψLeaf). Nous avons appliqué la méthode à dissipation thermique transitoire (TTD) développée par Do et Rocheteau (2002b) qui a plusieurs avantages mais n'avait pas été testée sur bois d'hévéa. La méthode TTD a été calibrée en laboratoire sur des segments de branches d'Hevea brasiliensis et de deux autres espèces (Mangifera indica and Citrus maxima). Les résultats fournissent une calibration linéaire unique indépendante des espèces étudiées (R² = 0.88, n = 276, P<0.0001). Une comparaison en plantation via un bilan hydrique du sol en saison sèche valide les ordres de grandeurs de transpiration ainsi estimés par les flux de sève. Les résultats démontrent une remarquable saturation de la transpiration au dessus d'un certain seuil d'évapotranspiration de référence (ET0), environ 2.2 mm day-1, indépendamment de la disponibilité en eau du sol (REW). Ensuite, le dessèchement du sol en saison des pluies provoque une chute marquée de la transpiration en dessous d'un seuil de 50% du REW dans l'horizon de surface du sol, ce qui correspond à ψpredawn autour de -0.45 MPa. La transpiration est réduite de 40% à REW 0.3 et 80% à REW 0.1. La valeur minimale de potentiel hydrique foliaire (ψminimum) en journée ensoleillée ne décroit pas en fonction du dessèchement du sol mais est stable autour de -1.95 MPa ce qui suggère un comportement iso-hydrique. La décroissance de la transpiration est essentiellement liée à la variation de gL. Les résultats durant la sécheresse saisonnière montrent étonnamment que les principes du modèle à limitation hydraulique tiennent malgré les variations de phénologie et de surface foliaire. De plus, les variations phénologiques ont peu influencé sur les détails des paramètres et relations du modèle. Finalement, le cadre du simple modèle hydraulique a été suffisant pour décrire correctement les principales variations de transpiration de l'arbre sous contrainte hydrique édaphique comme climatique. Un comportement iso-hydrique des arbres matures étudiés est démontré à la fois par les résultats expérimentaux et la modélisation.

From the Proceedings of the 1975 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 11-12, 1975, Tempe, Arizona / The response of saltcedar (Tamarix pentandra Pall.) to several antitranspirants was evaluated in laboratory, greenhouse and small -scale field studies using potted plants. Anti - transpirants may provide a treatment alternative to the eradication of saltcedar thickets for water salvage objectives. Transpiration rates were reduced by 23 to 44 percent for 7 to 20 days in the greenhouse, and by 18 to 32 percent for 2 to 8 days in the field. No serious damage to the plants was apparent. One of the most effective antitranspirants considered for a hypothetical saltcedar thicket and a hypothetical operational treatment program, based on estimated cost data, would result in reallocated water costing approximately 55 dollars per acre foot for a single treatment. About 19 acres of saltcedar thicket would have to be treated to provide one acre -foot of reallocated water in this case.

Une approche a plusieurs echelles a été développé afin de vérifier si les différences de Δ13C entre les genotypes de peuplier représentaient les différences d'efficience de transpiration à l'échelle des feuilles et la plante entière. Nous avons également vérifié la stabilité des différences génotypiques pour Δ13C dans le temps. Nous avons constaté que les différences génotypiques pour Δ13C pouvaient etre traduites comme la difference d efficience de transpiration a l echelle des feuilles ainsi qu au niveau de la plante entière. L amplitude de la variabilité de l efficience de transpiration a l echelle du plant etait plus grand par rapport à la variabilite a l echelle de la feuille, demontrant le rôle de la perte du carbone lors de la respiration diurne et nocturne (Φc) ainsi que l'eau perdue pendant la transpiration nocturne (Φw). La productivité génotypique augmentait avec l efficience de transpiration chez Populus deltoides × nigra, mais restait stable chez Populus nigra. Les valeurs absolues de l efficience de transpiration observees lors de cette etude etaient plus elevees que chez les autres especes. L enrichissement en 18O de la matiere organique (Δ18Olb) et de l eau (Δ18Olw) des feuilles correlait avec la variation de la conductance stomatique (gs) soit au niveau de l individu ou au niveau génotypique. Lors d une premiere experience nous avons montre que les valeurs de Δ13C restaient stables pour les genotypes Populus deltoides × nigra ages de 5 a 15 ans, avec un classement génotypique particulierement conservé pendant l etude. Toutefois, une seconde experience nous a permis de demontre que des arbres ages de 4 a 7 ans presentaient des valeurs de Δ13C significativement plus faibles que celles observees lors de la premiere experimentation, avec une augmentation progressive de ces valeurs avec l age. Nous concluons que, chez le peuplier, le Δ13C peut etre considere comme un estimateur fiable de l efficience de transpiration a l echelle du plant entier, et le classement genotypique établi chez de jeunes arbres pour Δ13C reste stable avec l'âge.

Bibliography: leaves 214-239. / xviii, 239 leaves : ill., maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The aim of this study is to identify the water use strategy of Malaleuca halmaturorum in response to salinity and waterlogging in the root zone and through this quantify groundwater use and the role of M. halmaturorum in the water balance. The water use strategy of M. halmaturorum is investigated in the saline ephemeral swamps of South Eastern South Australia to understand the effect of the wetland vegetation on the groundwater balance and the survival mechanisms and reasons for the decline in health of M. halmaturorum in the region. / Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1997