Factors controlling plasticity of leaf morphology in Robinia pseudoacacia L. II: The impact of water stress on leaf morphology of seedlings grown in a controlled environment chamber.

摘要

Context: The cause of morphological plasticity of leaves within the crowns of tall trees still debated. Whether it is driven by irradiance or hydraulic constraints is inconclusive. In a previous study, we hypothesized that water stress caused between-site and within-tree morphological variability in mature Robinia trees. Aims: To test this hypothesis, we designed an experiment to analyze the effect of long-term water stress on leaf growth of Robinia seedlings in a controlled environment. Methods: Two treatments were performed: well-watered (midday water potential, Psi _w=-0.45 MPa) and water-stressed ( Psi _w=-1.0 Mpa), which resulted in significant differences in physiology, relative growth rate, and the temporal progress of leaf growth. Results: Variation of leaf cell sizes among treatments was comparable to the variability previously observed in the field. However, values of leaf density and leaf mass per unit area tended to be lower in our controlled experiments than in the field, which may reflect differences between mature leaves of juvenile and adult trees. Conclusions: Our tentative conclusion is that leaf water stress may be the primary factor controlling morphological changes observed in the field, but further experiments are needed to document the relative importance of irradiance.