Dimensional variation of xylem elements in two trees from the Amazon Basin / Ademir Castro e Silva.

Tese (mestre) - Colorado State University, 1986

This study examined the fiber and vessel dimensions, and febril angle variation within Saccoglotis guianensis and Andira parviflora grown in the Amazon Basin. Samples were taken from seven levels in both species. Samples from branches for measurements of the dimensions were also taken. Individual measurements were done in macerated tissue samples, and prepared slides. In the radial direction both species showed an increase in fiber length with some irregularities from pith toward cambium. In both species the shortest fibers were found in the top of the stem. Vessel segments length initially increased and later declined gradually or with some fluctuations from pith towardas the cambium. Cell area and cell wall cross sectional area decreased towards the top of the tree while the ratio of cell-wass cross sectional area to the total cell cross sectional area was fairley constant along the tree. A high number of vessels per square millimeter were found at the top. Since 'Andira parviflora' has a greater quantity of parenchyma cells as well as a lesser number of vessel segments per square millimeter than' Saccoglotis guianensis' one may imply, based upon the relationship between structural elements and growth regulators as presented in the literature, that the concentration of auxin is higher in the later species. 'Sacccoglotis guianensis' has more vessel segments per square millimeter near the cambium. Both species showed an irregular decrease towards the top of the tree in fiber and vessel width. A strong negative correlation coefficient of fibrillar angle with fiber length was observed, with fibrillar angle getting small as fiber tength increases. Fibrillar angle decreased outward from the pith in both species. The average fiber and vessel lengths in the branches were smaller than those in the stem adjacente to the branches.