Leaf gas exchange in a clonal eucalypt plantation as related to soil moisture, leaf water potential and microclimate variables |
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Authors: | M S Mielke M A Oliva NF de Barros R M Penchel C A Martinez S da Fonseca AC de Almeida |
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Affiliation: | Departamento de Biologia Vegetal Universidade Federal de Vi?osa, 36571-000, Vi?osa, MG, Brazil e-mail: moliva@mail.ufv.br Tel.: +55-31-8992050, Fax: +55-31-8992580, BR Departamento de Solos, Universidade Federal de Vi?osa 36571-000, Vi?osa, MG, Brazil, BR Centro de Pesquisa & Tecnologia, Aracruz Celulose S.A. Aracruz, ES, 29197-000, Brazil, BR Produ?ao e Suprimento de Madeira, Aracruz Celulose S.A. Aracruz, ES, 29197-000, Brazil, BR
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Abstract: | In order to determine how environmental and physiological factors affect leaf gas exchange in a 9-year-old clonal eucalypt
plantation (Eucalyptus grandis Hill ex. Maiden hybrids) in the State of Espirito Santo, Brazil, the diurnal patterns of predawn leaf water potential (Ψpd), and leaf gas exchange were monitored from November 1995 to August 1996. Soil water content (Θ) and microclimatic variables
were also recorded. Most of the rainfall during the experimental period occurred from October to December 1995 and from March
to April 1996, causing a significant variation in Θ and Ψpd. A high positive correlation (r
2=0.92) was observed between Ψpd and Θ measured at 0.3 m depth from the soil surface. During conditions of high soil water availability, the maximum values
of stomatal conductance for water vapor (g
s) and net photosynthetic rate (A) were over 0.4 mol m–2 s–2 and l5 μmol m–2 s–1, respectively. The results showed that Ψpd and leaf gas exchange of the examined trees were susceptible to changes in the water content of the upper soil layers, where
the major concentration of active roots occur. Multiple linear regression analysis indicated that photosynthetic active radiation
(Q), vapor pressure deficit (VPD), atmospheric CO2 molar fraction (C
a), and Ψpd were the most important factors controlling g
s whereas Q and VPD were the main microclimatic variables controlling A.
Received: 5 November 1998 / Accepted: 10 November 1999 |
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Keywords: | Eucalyptus grandis Leaf water potential Net photosynthetic rate Stomatal conductance Water supply |
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