Journal Article

Effects of water stress on irradiance acclimation of leaf traits in almond trees

Gregorio Egea, María M. González-Real, Alain Baille, Pedro A. Nortes, María R. Conesa and Isabel Ruiz-Salleres

Edited by Ülo Niinemets

in Tree Physiology

Volume 32, issue 4, pages 450-463
Published in print April 2012 | ISSN: 0829-318X
Published online March 2012 | e-ISSN: 1758-4469 | DOI:
Effects of water stress on irradiance acclimation of leaf traits in almond trees

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Photosynthetic acclimation to highly variable local irradiance within the tree crown plays a primary role in determining tree carbon uptake. This study explores the plasticity of leaf structural and physiological traits in response to the interactive effects of ontogeny, water stress and irradiance in adult almond trees that have been subjected to three water regimes (full irrigation, deficit irrigation and rain-fed) for a 3-year period (2006–08) in a semiarid climate. Leaf structural (dry mass per unit area, N and chlorophyll content) and photosynthetic (maximum net CO2 assimilation, Amax, maximum stomatal conductance, gs,max, and mesophyll conductance, gm) traits and stem-to-leaf hydraulic conductance (Ks-l) were determined throughout the 2008 growing season in leaves of outer south-facing (S-leaves) and inner northwest-facing (NW-leaves) shoots. Leaf plasticity was quantified by means of an exposure adjustment coefficient (ε = 1-XNW/XS) for each trait (X) of S- and NW-leaves. Photosynthetic traits and Ks-l exhibited higher irradiance-elicited plasticity (higher ε) than structural traits in all treatments, with the highest and lowest plasticity being observed in the fully irrigated and rain-fed trees, respectively. Our results suggest that water stress modulates the irradiance-elicited plasticity of almond leaves through changes in crown architecture. Such changes lead to a more even distribution of within-crown irradiance, and hence of the photosynthetic capacity, as water stress intensifies. Ontogeny drove seasonal changes only in the ε of area- and mass-based N content and mass-based chlorophyll content, while no leaf age-dependent effect was observed on ε as regards the physiological traits. Our results also indicate that the irradiance-elicited plasticity of Amax is mainly driven by changes in leaf dry mass per unit area, in gm and, most likely, in the partitioning of the leaf N content.

Keywords: irradiance; leaf structural traits; mesophyll conductance; nitrogen-use efficiency; photosynthetic capacity; plasticity; Prunus dulcis; stem-to-leaf hydraulic conductance; stomatal conductance; water stress

Journal Article.  8885 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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