Wood and bark anatomy of the charismatic Wisteria vines (Leguminosae)

Wisteria is a legume genus composed of lianas with a disjunct distribution, occurring in temperate zones of eastern Asia and the eastern United States, being also introduced in numerous countries as an ornamental. The anatomy of the wood has been previously studied for W. sinensis and only some characteristics of the phloem have been reported for this species. Here we describe the overall wood and bark anatomy of four Wisteria species and identify diagnostic, informative anatomical features to sort them for identification purposes among the species of the genus. Samples were collected from natural, naturalized, and introduced populations and processed using traditional anatomical techniques, while a few samples were analyzed from photos available online. Wisteria species show conserved wood anatomy, even if species occur as far apart as Asia and North America. The presence of a cambial variant, vessel dimorphism, G-fibers, non-lignified axial, and ray parenchyma is common and is here interpreted as part of the lianescent syndrome. The subepidermal origin of the periderm is taxonomically informative within the subfamily. The few variable features that vary among species are the arrangement of narrow vessels: radial to dendritic pattern in the specie W. frutescens and arranged in clusters in the species distributed in Eastern Asia. Also, the ray cell composition: procumbent, square, and upright cells mixed through the body in the specie W. sinensis and procumbent to square cells in the body and upright in the margins in the species W. brachybotrys and W. frutescens.