The Role of Axillary Meristems in Coppice and Epicormic Bud Initiation in Araucaria cunninghamii

Axillary meristems are formed in all mainstem leaf axils of 2-mo-old hoop pines (Araucaria cunninghamii Aiton ex D Don) not occupied by first order branch buds. They have no bud-like organization or vascular connections and remain in this little differentiated and quiescent state unless stimulated to bud formation by release from apical dominance. With increasing plant age and hence increasing stem diameter, the meristems are not abscised via periderm formation, nor do they differentiate into bud primordia or break into fragments that lose their meristematic potentiality. Instead they maintain their structural integrity by elongating tangentially via infrequent anticlinal divisions within the meristem. Mean tangential dimensions for meristems from the base of 2-mo-old, 2-yr-old, and 4-5-yr-old hoop pines were 100, 200, and 740 μm, respectively. These results indicate why hoop pine, in contrast to the majority of conifers, has a pronounced ability to form coppice shoots.