Inflorescence and Flower Development in Musa velutina H. Wendl. & Drude (Musaceae), with a Consideration of Developmental Variability, Restricted Phyllotactic Direction, and Hand Initiation

Premise of research. Inflorescence and flower structure in the Musaceae is unique in the Zingiberales. The inflorescence lacks the obvious cincinnus structure that characterizes the order, and the flowers are unisexual. Previous studies were conducted using cultivated varieties and were carried out with sectioned material, which does not permit accurate developmental descriptions. Developmental study of a wild species with modern methods addresses these shortcomings and provides more accurate descriptions.Methodology. Young inflorescences and flowers were collected from botanical gardens in Hawaii and Australia and critical-point dried for observation with a scanning electron microscope.Pivotal results. All shoots and inflorescences have sinistrorse (left-handed) phyllotaxy, and the sequence of flower initiation is usually correlated with this pattern. Initiation begins on the cathodic side of the hand (opposite the direction of phyllotactic rise) and progresses anodically (in the direction of phyllotactic rise). Within this general pattern, the sequence of flower initiation is variable, even within the same inflorescence. Five patterns of initiation are reported, with additional variation within each pattern. Both male and female flowers have similar early developmental patterns but diverge at the time of petal/inner androecial formation. In male flowers the anterior side of the flower develops slightly ahead of the posterior, while in female flowers the posterior side develops slightly ahead of the anterior. While consistently present in the material analyzed here, these differences are not apparent at the time of gynoecial initiation or in the mature flowers.Conclusions. The banana inflorescence is another example of how higher-level phyllotactic patterns can influence the sequence of organ initiation at lower levels. Despite variability in the sequence of flower initiation in a hand, the best interpretation of the hand remains a cincinnus. Variability in inflorescence and floral development is rarely reported and may be more common than currently supposed