Data from: 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.研究背景。芭蕉科（Musaceae）的花序与花部结构在姜目（Zingiberales）中具有独特性。该科花序缺少姜目所特有的典型蝎尾状聚伞花序（cincinnus）结构，且其花为单性花。既往相关研究多采用栽培品种开展实验，并以切片材料为研究对象，无法实现精准的发育过程描述。本研究采用现代方法对野生物种开展发育学研究，以弥补上述缺陷，获得更为精准的发育描述。 研究方法。于夏威夷与澳大利亚的植物园采集幼嫩花序及花朵样本，经临界点干燥处理后，采用扫描电子显微镜（scanning electron microscope）进行观察。 关键结果。所有枝条与花序均呈左旋（sinistrorse）叶序（phyllotaxy），花原基发生序列通常与该叶序模式相关联。花原基起始发生于花序簇的阴极侧（与叶序上升方向相反），并沿阳极侧方向（即叶序上升方向）推进。即便在同一花序内，花原基发生的序列也存在变异。本研究共报道5种花原基发生模式，且每种模式内部仍存在额外变异。雄花与雌花的早期发育模式相似，但在花瓣/内层雄蕊群形成阶段出现分化。雄花的前侧发育略早于后侧，而雌花的后侧发育略早于前侧。尽管在本研究分析的样本中该差异始终存在，但在雌蕊群原基起始发生阶段或成熟花朵中，该差异并不明显。 结论。芭蕉花序进一步佐证了高阶叶序模式可影响低阶器官原基的起始发生序列。尽管单个花序簇内的花原基发生序列存在变异，但花序簇的本质仍应归类为蝎尾状聚伞花序（cincinnus）。花序与花部发育的变异现象鲜有报道，但其实际发生频率可能远超当前认知。