Root and stem anatomy of Sesbania rostrata

Anatomical investigation were made on the stem and root of Sesbania rostrata at different stages of growth. Xylem was found to be the first vascular tissue to differentiate. The root was tetrarch with four strands of xylem and four strands of phloem. One strand of xylem alternated with one strand of phloem. The epidermis was single layered. Beneath the epidermis there were cortex with some tannin cells. The cambium appeared at the basal part of the root and graduaHy it extending towards the root apex. The phellogen appeared in the deeper cortex and produced 45 layers of cork cells and 2–4 layers of phelloderm. In the stem, the epidermis Was single layered. Beneath the epidermis there were 10–12 layers of cortex with lots of tanniniferous cells. The vascular bundles were of two types, small and large with bundle caps. In the large vascular bundle, the primary phloem consisted of a number of sieve elements while in the small bundle there were parenchymatous tissue with or without functional sieve element. The large vascular bundle contained 5–7 strands of xylem while the small bundle contained 1 or 2. The cambium differentiated in between xylem and phloem of the primary structures of the stem. It became active and gave rise to secondary phloem and secondary xylem. The vessels were small and big. The smaller vessels lay in between or among the big vessels. Most of the vessels were solitary. Among the elements of secondary phloem, axial parenchyma was found to occupy the major area. The periderm developed one after another from deeper cortex.