Leaf surface wettability and fatty acid composition of Arbutus unedo and Arbutus andrachne grown under ambient conditions in a natural macchia

Abstract

Features of the adaxial and abaxial surface microstructure of Arbutus unedo L. and Arbutus andrachne L. are evaluated as possible consistent parameters contributing to the wetness of leaves. The abaxial leaf surface of A. andrachne and A. unedo was determined to be more hydrophobic than the adaxial leaf surface. Hydrophobicity may be of particular importance for the ecophysiological status of the hypostomatic leaves of both Arbutus species, which exhibit a long lifespan and are exposed to various environmental stimuli. Water repellence may also be correlated to the increased presence of surface wax. Lipid analysis of the leaves of both plant species revealed an abundance of α-linolenic acid, with palmitic acid as the second major contributor, followed by linoleic and oleic acid. Oleic and linoleic acid were present in slightly larger percentages in A. andrachne compared with A. unedo, whereas myristic, palmitic and α-linolenic acids were found in elevated percentages in A. unedo. The fatty acid composition analysis of the leaf wax of A. andrachne and A. unedo ranged from C16 to C26, with fatty acids of an even longer chain length detected in the case of A. andrachne. Despite the similar fatty acid composition of total lipids, the composition of the wax fraction showed differences between the two Arbutus species, which may partly contribute to the foliar surface properties of the two species.