ABSTRACT
Intact plants possessing leaves of different physiological ages, meristems in different states of activity, and a root system are certainly not ideal for determining whether or not correlative influences are basic to flower initiation. Investigations with several herbaceous perennials requiring a chilling treatment for flower initiation show convincingly a role for apical dominance in the control of flowering. The influence of apical dominance on flowering has been found in several other perennials, including orchids and woody species. Species with axillary flowers are perhaps the most interesting for determining the changes in sensitivity of meristematic tissues towards flower stimuli as a function of the plastochron stage. In Xanthium and perhaps other species, buds might even be required in addition to mature leaves for photoinduction to proceed. Flowering of excised vegetative apices depends on factors from young leaves, scales or cotyledons. Flower formation in organ pieces initially devoid of primary meristems is similarly influenced by complex tissue interactions.
