Influence of bud break and apical meristematic tissue competence during cloning mature trees of conifers

This review paper highlights the influence of bud break and apical meristematic tissue competence in inducing embryogenic tissue during cloning mature trees of conifers. Bud burst depends on dormancy release by chilling or heat due to increase in the day temperature, and accumulation of thermal time above a species-specific threshold. The buds collected immediately after the bud burst were found very responsive for the in vitro cloningof P. kesiya, P. roxburghii and P. wallichiana, P. patula, and P. sylvestris, This might be duethe activation of the apical meristematic cells showing active growth of shoots in most of theconifers. The active dividing and totipotent cells might be positioned only at the cambiallayer of the apical meristematic tissue in conifers, so that their growth and division leads to acontinuous flow of progeny cells. These cambial layer cells under stress conditions undergodifferentiation and leading to the embryogenic pathway in conifers