The transmitting tract in Gloriosa superba: structure, pistil exudate and pollen tube growth

Abstract

The structure of the pistil exudate, transmitting tissue and pollen tube growth of Gloriosa superba L. were studied. Flowers are protogynous, as the stigmas become receptive one day prior to anther dehiscence, and remain receptive for at least four days. Neutral red and auramine O proved to be useful for the indication of stigma receptivity. The stigma is wet while the papillae and canal cells form slight interior cell wall ingrowths reminiscent of transfer cells. Pistil exudate is mostly lipidic, confirmed by the prevalence of endoplasmic reticulum in the cytoplasm. The canal exudate includes substances derived from degenerating canal cell walls and lipid-like vesicles breaking down into fine fibrillar matter possibly associated with the pollen tube cell wall. Pollen tubes grow in close association with the stylar secretion, reaching most ovules, even though pollen tube numbers decrease on their way down the stylar canal. Callose deposition in the nucellus of some self-pollinated ovules could be indicative of a partly pre-zygotic gametophytic self-incompatibility system.