Relationships between transpiration, stomatla damage and leaf wettability in declining beech trees

In order to determine the relationship between transpiration, stomatal damage and leaf wettability in adult beech trees (Fagus sylvatica L.) in situ, sample leaves were gathered from healthy trees and from declining trees, both at the beginning and at the end of the growing season. Four parameters were assessed in each leaf: transpiration in the field, transpiration in the laboratory after rehydration, stomatal damage index, and leaf-water drop contact angle. The results showed that the transpiration was linked to the health status of the tree only when the external conditions were least favourable, i.e. in the month of June in the field. During the season the index of stomatal damage increased considerably in declining trees, while the drop contact angle decreased. Linear regression between the transpiration and the stomatal damage indix did not show any significant correlation, thus suggesting - at least in the environmental conditions prevailing in thi experiment - structural alterations in the stomata were not capable of modifying the transpiration capacity. Lastly, contact angle data did not correlate significantly with either the transpiration or the stomatal damage index.