Are sclerophylls and malacophylls hydraulically different ?

Abstract

This work tests the hypothesis that sclerophylls (i.e. hard-leaved species) would be less efficient than malacophylls (i.e. soft-leaved species) in terms of water transport through the stem as well as within the leaf blade. Mean leaf surface area (AL), leaf specific mass (LSM) as well as shoot (KWL), stem (KSL) and leaf (KLL) hydraulic conductances were measured in eight Mediterranean evergreen sclerophylls and eight temperate deciduous malacophylls. No difference was observed between the two groups in terms of KLL and of the contribution of leaves to the overall shoot hydraulic resistance. Leaves represented in all cases 48 to 90 % of the shoot hydraulic resistance, suggesting that the sclerophyllous habitus does not per se lead to low efficiency in water transport within the leaf blade. A weak negative relationship (r2 = 0.252) appeared to exist between KSL and LSM. This might provide an explanation for the lower growth rates of sclerophylls with respect to malacophylls.