Leaf structure, microanalysis and characterization of the latex protein profile of Pachystroma longifolium (Nees) I.M. Jonhst. (Euphorbiaceae) in a seasonally dry Atlantic Forest

Abstract

Pachystroma longifolium is an evergreen species of Euphorbiaceae that occurs in tabuleiro forest, a type of lowland Atlantic Forest. The site chosen for this study was a fragment of tabuleiro forest that has a history of being selectively logged for timber. P. longifolium is very successful at colonizing disturbed areas in this forest fragment in comparison with preserved fragments. In the present work, which was based on using different microscopy (electron and light microscopy, X-ray analysis) and biochemistry techniques, we describe the leaf and latex traits of P. longifolium and their role as defense mechanisms against desiccation and herbivory. Our results suggest the richness of P. longifolium populations, in the disturbed forest area studied, is primarily a consequence of unpalatable leaves because of an abundance of calcium oxalate crystals in the subjacent epidermis; the presence of phenolic compounds in the adaxial surface; and a laticifer system that contains a complex mixture of proteins, which provides resistance to herbivores. In addition, this species is resistant to desiccation during dry periods because of an extensive amount of wax that occurs on the outer cell walls of the epidermis, and its ability to retain water because of a biseriate epidermis.