1. Introduction

Axillary buds are usually present in the axil of each leaf and every bud has the potential to develop into a shoot. In nature these buds remain dormant for various periods. The species with strong apical dominance show the growth of axillary buds into shoot only if the terminal bud is removed or injured. The phenomenon of apical dominance is regulated by the interplay of growth regulators. The application of cytokinin to the axillary buds can overcome the apical dominance effect and stimulate the lateral buds to grow rapidly in the presence of terminal buds. If the exogenous growth regulator diminishes the lateral shoot stop growing.

2.  Rate of shoot multiplication

In plant tissue culture, the rate of shoot multiplication can be determined by enhanced axillary branching. Due to continuous availability of cytokinin, the shoots formed by the bud, a priori present on the explant (nodal segment or shoot-tip cutting), develops axillary buds which may grow directly into shoots. This process may be repeated several times and the initial explant transformed into a mass of branches. There is a limit to which shoot multiplication can be achieved in a single passage, after which further axillary branching stops. At this stage, if shoots are excised and planted on a fresh medium of same composition, the shoot multiplication cycle can be repeated. This process can go on indefinitely, and can be maintained throughout the year independent of the season and the region.

In some plants, it may not be possible to break apical dominance by the application of growth regulator compositions, and the bud present a priori on the initial explant grows into an unbranched shoot. The rate of shoot multiplication in such cases would depend on the number of nodal cuttings that can be excised from the newly developed shoot at the end of each passage. With this alternative method of enhanced axillary branching, 6-7 fold shoot multiplication every 4-6 weeks could be achieved in the plants with strong apical dominance.