Leaf epidermal features of Salix species (Salicaceae) and their systematic significance

Abstract

The classification of the genus Salix has historically been intrinsically difficult due to its propensity toward plasticity and high variation in diagnostic morphological characters. We investigated leaf epidermal characteristics, focusing on the stomatal apparatus because it may provide critical insights into the evolution and taxonomy of Salix and its closely related genera. Light microscopy was used to examine the leaf epidermal features in 32 taxa of Salix. Characters such as shape, size, and density of stomatal complexes were very useful in differentiating Salix species. Variation in features of stomatal apparatus in Salix is wider than previously known. Moreover, the type of stomatal complex proved to be very helpful in discriminating Chosenia as members of the genus Salix. The results of the present study support the placement of Chosenia within Salix and the combining of subgenera Chamaetia and Vetrix because of similarities in their unique stomatal apparatus.