FLORAL DEVELOPMENT IN OTTAWA AND FLOREX RED CLOVER TRIFOLIUM PRATENSE (PAPILIONOIDEAE: LEGUMINOSAE)

Abstract

Floral development in Florex and Ottawa cultivars of red clover (Trifolium pratense L.: Leguminosae) was examined by scanning electron microscopy. No differences between the two cultivars were found. The terminal inflorescence is initiated in the axil of the penultimate bract before the final bract is initiated. After initiation of the final bract, the remnant apical dome is transformed to become the least mature part of the inflorescence dome. Subsequent inflorescences are initiated laterally in basipetal sequence. Inflorescence development is zygomorphic. This leads to an unusual pattern of floret initiation, the oldest florets resting basally and proximal to the penultimate bract. Florets develop with zygomorphic symmetry, each whorl of floral organs developing unidirectionally from the abaxial side. Initiation of the adaxial organ of each whorl is delayed until the abaxial organ of the succeeding whorl has been initiated. Thus there is overlapping development of the whorls of organs. The antepetalous stamens arise in close association with their respective petal primordia. As development proceeds, the corolla tube and the staminal tube exhibit basal zonal growth. In the mature flower, above the distal zone of fusion of the keel petals, marginal cells project and interlock, producing a pollination mechanism that can be sprung by the pollinator.