Unravelling the roots of lianas

Woody vines collectively known as lianas are fundamental components of tropical forests but their root structure is largely unexplored. Stems of Sapindaceae display diverse architectures and an anatomical pattern typical of climbing plants. Bastos et al. explore the root structure of well-developed roots in numerous lianoid genera of this family.

Macroscopical anatomical patterns of the roots of Sapindaceae lianas. (A) *Serjania communis*, showing absence of cambial variant. Type (1), simple. (B–D) Presence of cambial variants and occasionally additional vascular formations. (B) *Urvillea rufescens*. Type (2), lobed. (C) *Serjania lethalis*. Type (8), xylem furrowed by phloem wedges (arrowheads). (D) *Serjania caracasana*. Type (8), xylem furrowed by phloem wedges (arrowheads) with additional presence of neo-formed peripheral vascular cylinders (arrows).

All roots exhibited a lianescent anatomy marked by the presence of vessel dimorphism but most lacked cambial variants. Exceptions were observed such as the lobed roots of Urvillea rufescens and phloem wedges in Serjania lethalis and Serjania caracasana. Neo-formed peripheral vascular strands and cylinders were common in mature roots of Serjania caracasana. Vascular connections were found uniting peripheral and central vascular cylinders through phloem wedges, as revealed by anatomical and micro-CT analyses. The study provides an overview of the diverse traits, architectural structures and underlying mechanisms of lianas’ roots.

This paper is part of the Root Biology Special Issue.