LIANA ANATOMY: A BROAD PERSPECTIVEON STRUCTURALEVOLUTION OF THE VASCULAR SYSTEM
Angyalossy V; Pace M.R; Lima A.C
Ecology of Lianas
The vascular system of lianas exhibits a number of shared features that result from convergent evolution and are independent of their taxonomic affinities. In this chapter we explore the vascular system of lianas in major lineages addressing different aspects of their anatomy development seasonal growth and evolution. Since lianas are twining plants that climb in the search of light various special features favor this habit and guarantee an efficient fluid conduction through-out their long stems. Both xylem and phloem of lianas are conspicuous for their wide conducting cells. In xylem it is also common to find a reduced volume of numbers associated with an increased amount of axial parenchyma. The flexibility required to twine seems to have been facilitated by the widespread presence of variant secondary growth which derives from the activity of one or multiple cambia. The evolution of cambial variants in different lineages seems to have led to an increase in anatomical complexity in lineages in which variants occur. Cambial variants also affect xylem differentiation and seasonal response to environmental cues. Lianas may have active cambia fora very short period of time from two months to up to a year most likely a taxon-dependent feature. The vascular system of lianas provides a wealth of features to explore the link between habit development and the evolution of complex anatomies.