ORIGIN AND DEVELOPMENT OF AXILLARY BUDS IN HIBISCUS CANNABINUS

Abstract

BRANCHES PLAY an important role in the development of the plant and also in its propagation, and where there is little dominance of the shoot apex they are virtually responsible for the size and form of the plant. They possess a structure fundamentally similar to that of the main axis and pass through essentially the same successive stages of development as the leaves in the axils of which they arise as axillary buds. The buds are, therefore, suitable for comparing the mode of differentiation of procambium and vascular tissues with that in the main shoot apex. For these reasons, they are chosen for studies of experimental morphogenesis which have brought to light several factors responsible for bud development on the one hand and the interrelationships of bud, leaf and stem on the other (Wardlaw, 1952, p. 416). Apart from these aspects, the study of the development of buds has special significance with regard to the improvement of crops (Sharman, 1945; Kundu and Rao, 1954). In view of the growing importance of this study, there is at this stage a need for wider and more systematic survey of possible types of development. Majumdar and Datta (1946) have distinguished two types of bud development, axillary and foliar. They further suggested that the axillary type may be characteristic of monocotyledons; the foliar type, of dicotyledons. However, later studies have shown that in both dicotyledons and monocotyledons, the development of buds on aerial shoots is predominantly axillary. In the majority of cases, bud initials have their origin in the apical meristem or very near to it and are isolated during growth and vacuolation. Even in apparently normal development of such axillary buds, certain interesting variations exist but often they either are not recognized or their significance is not sufficiently stressed. Esau (I1953, p. 107) has pointed out that the detached meristems (Wardlaw, 1943a) are situated on the stem slightly above the axils. Other variations also have been reported in some varieties of Corchorrus capsularis (Kundu and Rao, 1954). However, very few cases of bud development are reported which depart so much from the normal as does that in Hibiscus cannabinus. The differentiation of vascular tissues in axillary buds has been studied in a few cases only (Miller and Wetmore, 1946; Garrison, 1949a, b). Besides the origin and development of the bud, differentiation of the vascular system is considered in this paper. MATERIALS AND METHODS. Although Hibiscus cannabinus has been known as a fibre-yielding plant