Floral development and anatomy of Moringa oleifera (Moringaceae): What is the evidence for a capparalean or sapindalean affinity

Abstract

Floral development and anatomy of Moringa have been investigated in the context of the disputed view of a capparalean affinity. Flowers arise in terminal or axillary panicles. Sepals arise sequentially and petals simultaneously. Antepetalous stamens arise simultaneously and precede the antesepalous staminodes, which emerge sequentially. Within their respective whorls, the petals and stamens become twisted along different orientations. The gynoecium develops as a ring primordium on which three carpellary lobes become demarcated simultaneously. A saccate ovary bears numerous ovules on a parietal placentation and is topped by a hollow style. The interpretation of laminal placentation is denied. Monothecal anthers are formed by the failure of one half to initiate. The flowers present a peculiar form of zygomorphy running transversally from the petal between sepals 3 and 5 to sepal 4. The shape and position of petals and stamens is related to a pollen presentation mechanism with bowl-shaped anthers on different levels. The floral anatomy also reflects the zygomorphy of the flower. Although Moringa shares important morphological features with certain members of the Sapindales and Capparales, differences in ontogeny make a close relationship with either Capparales or certain Sapindales appear uncertain.