Caracterização do câmbio e do lenho de árvores de Schizolobium parahyba var. amazonicum (Huber ex Ducke) Barneby de plantação em clareira da Amazônia

Abstract

This study aimed at describing the anatomy of the vascular cambium and wood of Schizolobium parahyba var. amazonicum, including the cellular variation between planted trees and the longitudinal variation within the tree at different heights. Furthermore, it also aimed at determining the effect of the cambium cells structure on the anatomical characteristics of the wood. We extracted samples containing cambium, xylem and recently differentiated phloem by using a non-destructive method. A total of nine trees up to 1.30 m from the ground were studied in order to evaluate the variation between planted trees. Also, three trees at three different levels of height were studied in order to evaluate the axial variation of the cambium and the wood. The sampling was carried out in a single growing period. Variations of the dimensions of the cells were analyzed from the histological sections of the cambium and the wood and functional relations were established between the dimensions of the cambium and the wood. The vascular cambium presented fusiform initials and non-stratified cambial radius; activities were also evidenced during the study period. The average length, fiber wall thickness and vessel diameter were higher than the results of other studies of wood of species from homogenous plantations. Statistically significant differences were observed for the size of the cambium and wood cells between the planted trees. A reduction from the base to the top of the trees was also observed in the cambium as well as in the number of cell layers and width of the cambium zone, length and radial diameter of the spindle cells; a reduction also occurred in the length of the cambium radius and in the wood, as well as for the height and width of the radius. However, an increase of the average values from the base to the top of the trees was observed for the width of the cambium radius. The height of the radius of the wood (number of cells) was positively correlated with length of the cambium radius in μm (r = 0.71), and in number of cells (r = 0.79). The length of the fusiform initials correlated positively with the length of the vessel elements (r = 0.78), the length of the fibers (r = 0.74), the height of the wood radius in μm (r = 0.79) and in the number of cells (r = 0.92). The results indicate that the size of the wood cells of the species are strongly dependent on the structural changes of the cambial initials due to tree growth the age difference between the base of the cambium and the top of the trees.