Size of the Chrysanthemum Shoot Apex in Relation to Inflorescence Initiation and Development

The size of the apical dome of Chrysanthemum morifolium Ramat. at the transition to inflorescence initiation in continuous light (long days) was not systematically influenced by either the temperature or the irradiance under which the plants were grown. It was generally 0.26 mm in diameter and c. 3.6 × 10−3 mm3 in volume when the first bract was initiated. The dimensions of the apical dome of plants in short days were only slightly smaller at this stage. Similarly, each step in the further development of the chrysanthemum inflorescence was associated with a narrow range of apex sizes, indicating that inflorescence initiation and development are closely related to apex size.