Cortical origin of the successive cambia in the stems of the charismatic temperate lianescent genusWisteria(Fabaceae) and its systematic importance

Abstract Successive cambia are not commonly reported in lianas from temperate zones, but previous studies have pointed to their presence in Wisteria, albeit with controversy concerning their origin. The aim of this work was to elucidate the origin and development of the successive cambia in stems of Wisteria and to check whether this cambial variant is shared by the entire genus. We use detailed anatomical analyses to identify the anatomical ontogeny of the successive cambia. Our results reveal that all species studied share the presence of successive cambia. For several years, the secondary growth is regular; with the development of the cambial variant occurring outside from the pericyclic fibres in the cortical parenchyma. This occurs in patches, which commonly merge, resulting in many different configurations of this cambial variant in the stem. Successive cambia are probably a synapomorphy of Wisteria, and here we highlight the importance of the topological position of the pericyclic fibres in identifying the origin of this cambial variant in the genus.