Foliar Water Uptake Capacity in Sun and Shade Leaves of Fagus sylvatica L.

Foliar water uptake (FWU) is emerging as a key strategy for coping with drought, prompting more and deeper investigation into its role. This study examines the FWU dynamics by a series of time-dependent submersion experiments in sun and shade beech (Fagus sylvatica L.) leaves, a species known for its drought sensitivity. The results showed distinct FWU capacities, linked to their varying leaf water potentials, indicating that this factor is the driver for foliar absorption. Both sun and shade leaves experienced a proportional increase in leaf water content subsequent to FWU, with the same increment across leaf types after normalising for leaf water potential. Furthermore, results uncovered distinct foliar absorption dynamics between sun and shade leaves, pointing to specific absorption strategies. While sun leaves were able to absorb more water, they approached saturation more gradually compared to their shaded counterparts. This divergence in water management strategy also reflects the morpho-anatomical adaptation of sun and shade leaves to their respective microclimates.