Axillary bud traces in certain dicotyledons

Abstract

The ontogenetic development of the axillary bud traces in two species of the family Verbenaceae, Clerodendrum inerme L. and C. splendens Gaertn. and one species of the family Myrtaceae, Syzygium cumini L., is described.Initially the two bud traces differentiate as branches of the leaf trace complex of the subtending leaf. Its further course in the bud may be due to direct differentiation of bud meristem cells as in Syzygium, or by the process of dedifferentiation and redifferentiation of certain sectors of the ground meristem intervening between the bud and the leaf trace of the subtending leaf as in Clerodendrum. Consequent to their further differentiation in the bud, the development of the primary vascular meristem of the bud occurs, initially as two arcs, later as an incomplete ring, and finally as a complete ring. It consists of residual meristem and procambium strands. The procambium strands form an anastomosing pattern of primary vascular system of the bud. Their ultimate origin can be traced to the two bud traces.An incorrect histogenic picture of the developing primary vascular system of a growing bud is obtained if one considers the vascular configurations of an arc or a complete or incomplete ring as bud traces. This histogenic development is a result of morphogenic interaction between the apical meristem of the bud and acropetally developing procambium strands of the bud trace. The vascular structures described as arcs, horseshoe-shaped, or ring are the phasic histogenic expressions of the gradual differentiation of the primary vascular system of the bud.