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Factors controlling plasticity of leaf morphology in Robinia pseudoacacia : III. biophysical constraints on leaf expansion under long‐term water stress
Author(s) -
Zhang Yanxiang,
Equiza Maria Alejandra,
Zheng Quanshui,
Tyree Melvin T.
Publication year - 2011
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.2011.01504.x
Subject(s) - turgor pressure , robinia , relative growth rate , osmotic pressure , horticulture , growth rate , botany , biology , chemistry , mathematics , geometry
In this article, we measured the relative growth rate (RGR) of leaves of Robinia pseudoacacia seedlings under well‐watered and water‐stressed conditions (mid‐day Ψ w = leaf water potential estimated with a pressure bomb of −0.48 and −0.98 MPa, respectively). Pressure–volume (PV) curves were done on growing leaves at 25, 50 and 95% of the mature size (growth stage) in order to compute solute potential (Ψ) and turgor pressure (Ψ P ) as a function of Ψ w . The PV curves and diurnal measurements of Ψ w and RGR allowed us to evaluate the parameters (cell wall extensibility m and growth turgor threshold Y) of the Lockhart equation, RGR = m(Ψ P − Y), at each growth stage. Our data showed that m and Y did change with leaf age, but the changes were slow enough to evaluate m and Y on any given day. We believe this is the first study to provide evidence that the Lockhart equation adequately quantifies leaf growth of trees over a range of time domains. The value of m linearly declined and Y linearly increased with growth stage. Also, mild drought stress caused a decline in m and increase in Y relative to controls. Although water stress caused an osmotic adjustment which, in turn, increased Ψ P in stressed plants relative to controls, the RGR and final leaf sizes were reduced in water‐stressed plants because of the impact of water stress on decreased m and increased Y.