Stipular colleters in Psychotria nuda (Cham. & Schltdl.) Wawra (Rubiaceae): micromorphology, anatomy and cristals microanalysis

Colleters are secretory structures, with a protective function, that occur in different organs and in many Angiospermae families. The aim of this work was to describe the anatomy and micromorphology of colleters present in Psychotria nuda (Cham. & Schltdl.) Wawra as well as analyze the structure and composition of crystals from the central axis of the structure under study. The material was collected at the Tinguá Biological Reserve and processed according to usual techniques for light and scanning electron microscopy. The colleters are of the lachrymiform type, with an elongated central axis, formed by fundamental parenchyma, sheathed by a palisade layer, responsible for the secretion. Raphid crystals were observed in the central axis of the colleters. By X-ray microanalysis it was possible to show calcium predominance in these structures

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

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