Development of pollen grain in yellow passion-fruit (Passiflora edulis f. flavicarpa; Passifloraceae)

To clarify events occurring during pollen grain formation in yellow passion -fruit (Passiflora edulis f flavicarpa), floral buds were collected at diff erent stages of development. After bracket, petal and sepal removal the ant hers were fixed, dehydrated, embedded in paraffin wax, sectioned at 10 mu m and after differential dying with safranin O and fast green, mounted in Ca nada balsam and observed under optical microscope. Formation of the male ga mete followed the normal pattern for angiosperms. Observation covered final sporogenic mass phase up to pollen grain formation; microsporangium tissue modifications were also observed. Microsporogenesis was characterized by s porogenic tissue differentiation in microsporic mother cells, followed by m eiosis and resulting in tetrads. Microgametogenesis began with callose micr ospore release, subsequent mitosis, in addition to radial and tangential ta petum wall degradation, parietal layer compression nearer to the tapetum an d endothecium widening, terminating in mature pollen grain formation.