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Water use efficiency and "1"3C discrimination in Eucalyptus globulus Labill. genotypes / Eficiencia de Uso da Agua e Discriminacao do "1"3C em Diversos Genotipos de Eucalyptus globulus Labill

  • Osorio, Julio Armando P. da Cunha
Publication Date
Jan 01, 1994
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The objective of this work was the study of genetic variability in water use efficiency and the effects of water deficits on growth and productivity of genotypes of Eucalyptus globulus Labill. Potted plants of clones and provenances were selected because of contrasting inherent growth capacity and were grown in a greenhouse under well-watered and moderate soil water deficit conditions. Daily time-courses of leaf gas exchange and leaf water potential (at pre-dawn and midday) were determined at different times during the experiments. Biomass production and leaf area were determined at the beginning and end of the experiments. Leaf tissue grown after the onset of water deficits was analysed for "1"3C/"1"2C ratio against the PeeDee Belemnite standard (#delta#"1"3C). Long-term water use efficiency (i.e., biomass per unit of water transpired, WUE) was significantly increased by water deficit and was positively correlated with #delta#"1"3C. Long-term WUE was well correlated with the quotient of the daily integrals of carbon assimilation rate and stomatal conductance (A/g). Because the photosynthetic capacity was not significantly affected by water deficits, we may assume that most of the changes in A/g with water deficit resulted from stomatal closure leading to a lower average internal CO_2 partial pressure (#rho#i) and therefore to more #delta#"1"3C. The changes in WUE (and consequently #delta#"1"3C) were negatively, but closely, correlated with variables that are normally positively related to growth, such as specific leaf area (SLA) and the ratio of biomass produced to light intercepted (#epsilon#), and was positively related to the amount of carbon per unit leaf area #rho#, which is usually negatively correlated with relative growth rate (RGR). Discrimination for "1"3C may be used to select for genotypes that maintain a high productivity per unit of water available, under moderate soil water deficits / Available from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a Tecnologia / SIGLE / PT / Portugal

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