Abstract
The process of inflorescence development from flower initiation to anthesis was observed in a dichasium, kalanchoe (Kalanchoe blossfeldiana Poelln.) 'Red Glow'. Our major interests were why, when, and how florets aborted. To describe and analyze inflorescence development, an inflorescence was classified into 4 structural hierarchies: An inflorescence, an inflorescence unit, a module, and a phytomer. Remarkable regularities in inflorescence development of kalanchoe were observed as follows.
1. Floret primordia regularly differentiated by dichasial branching in the inflorescence unit.Some of florets which differentiated at higher orders failed to develop and aborted as they became macroscopic. Competition for assimilates among florets might be responsible for ther abortion.
2. The branching order at which florets abortion began and the number of florets per inflorescence unit were significantly correlated with the diameter of the inflorescence unit axis.
3. In inflorescence units and modules, there were an exponential relationship between the fresh weight (W) and the axis diameter (D), represented by the equation W = 0.0967D3.13.
4. There was a close relation between the position of florets and their abortion. After several dichasial branching, the branches of the inflorescence unit partly tended to form a uniparous scorpioid cyme, generating the zigzag branching by a regular abortion of florets.
5. Module development was also influenced by its position in the inflorescence. When modules developed outwardly and had sufficient space to expand, they were vigorous and eventually produced many florets. However, if the modules developed inwardly and competed with adjacent ones for space, their growth stopped at lower branching orders. When growing conditions were favorable for both modules, they developed symmetrically. Consequently, the inflorescence became almost flat because the florets were horizontally oriented.
