Xylem structure of successive rings in the stem of abuta grandifolia (Menispermaceae) a statistical approach

Abstract

Abuta grandifolia (Mart.) Sandwith varies in habit and can be a shrub, tree or liana. Its stem shows successive cambia that produce secondary phloem and xylem. This study analyses qualitative and quantitative differences between the secondary xylem of lianas and shrubs of A. grandifolia, as well as between the successive rings within each habit category. The lianas had wider vessels, shorter vessel elements and thinner fibre-tracheid walls. In the first five successive rings, lianas showed an increase in vessel diameter and fibre-tracheid length, while fibre-tracheid wall thickness decreased. The shrubs showed an increase in the diameter and length of vessel elements and length of fiber-tracheids. In qualitative features the secondary xylem of lianas and shrubs did not differ, except in their type of parenchyma (axial parenchyma diffuse in the liana habit and diffuse to diffuse in-aggregates in the shrub habit). Since significant quantitative differences were found between the successive rings, the first vascular ring is recommended for comparing both habits. Whether this is generally valid in Menispermaceae requires further study.