Cambial Anatomy, Development and Structural Changes in the Wood of Teak (Tectona grandisL.f.) Associated with Insect Defoliation

Abstract

Periodicity of vascular cambium, development and structural changes in the juvenile wood of teak (Tectona grandisL.f.) associated with insect defoliation were examined histologically. In affected trees cambial activity and development of secondary xylem began in June and reached its peak in August. Activity declined suddenly in September when the leaves were highly damaged by the insects and sluggish growth was observed until the cessation of cambial cell division in November. In the normal trees, cambium cells, which began to divide in June, culminated in August-September, activity declined in November and the cambium was surrounded with mature xylem and phloem in December. Differentiation of xylem and phloem occurred simultaneously, whereas a phloem development ceased first followed by xylem in both normal and affected trees. Xylem is ring porous with distinct growth rings. Teak plants affected by insect defoliation showed narrow growth rings while in normal trees such narrow rings were observed occasionally. As compared to normal trees, vessel lumen diameter remained more or less the same but its frequency was more in the affected trees. Other dimensional details like length, width, lumen diameter, frequency, etc., of individual xylem elements also showed considerable variation as compared to normal trees.