Activation of cambial layer influences cloning of mature trees of conifers

The shoot apical meristems are organized pools of undifferentiated or embryonic cells (stem cells) maintained by a dynamic balance between cell division and differentiation. On the basis of our mature tree cloning of pines, it is found that actively dividing and totipotent cells (stem cells) are positioned only at the cambial layer of the apical meristematic tissue in conifers, so that their growth and division under in vitro conditions leading to a continuous flow of progeny cells. These progeny cells (stem cells) under stress conditions (cold/heat) undergo differentiation due to signal activation in cambial region and leading to the embryogenic pathway in conifers. On the other hand the rest of the layers (epidermis, cortex region and central pith or medulla) of the transverse thin section of shoot apical meristems of mature trees have induced non--embryogenic tissue under in vitro conditions in conifers