Botanical studies on two species of senna mill.

Most of Senna species including those under study formerly belonged to the genus Cassia until reassigned recently to follow the genus Senna, but this process is not entirely complete and some corrections may still take place. Thus, any new information about Senna plants are urgently to be welcomed. It is aimed in this study to bring to light more information about the morphology and anatomy of two Senna species belong to the family Caesalpiniaceae, namely; Senna occidentalis (L.) Link and Senna sophera (L.) Roxb. This would be an effort to proper delimitation of these species in the genus Senna which are of great interest from an economic and medicinal point of view. The morphology of vegetative growth included: plant height, length and diameter of the main stem, number of internodes of the main stem, number of primary branches developed on the main stem, lengths of primary branches at maturity, fresh weight of leafless shoot per plant, total number of leaves per plant, total leaf area per plant and fresh weight of leaves per plant. Moreover, keen observations and descriptive morphology of the root and the shoot were under consideration. The morphology of reproductive growth included: flower bud differentiation, full blooming, fruit set and maturity. In addition, the yield characters at harvest time were investigated; i.e., number of matured dry pods per plant, number of seeds per pod, number of seeds per plant, yield of matured dry seeds per plant and specific weight of seeds. The current investigation was also concerned with the histological features of the two Senna species. The anatomical structure of different vegetative and reproductive organs was investigated, weekly or fortnightly, throughout the whole growing season. Studied organs included main root, main stem (represented by shoot apex, apical and median internodes), different foliage leaves developed on the main stem and on lateral shoot; including lamina and petiole, epidermal peel and trichomes, flower bud, fruit and seed. Histological features of various organs of the studied Senna species were analyzed microscopically and photomicrographed. Moreover, ultrastructural features of the seed coat were investigated using scanning electron microscope.