Pollen Biology

Abstract

Pollen grains represent male gametophytes and are the male partners in sexual reproduction. Following anther dehiscence, pollen grains are exposed into the atmosphere. At the time of shedding, pollen grains contain either 2 cells (a large vegetative cell enclosing the generative cell) or 3 cells (vegetative cell enclosing the two male gametes formed by the division of the generative cell) (Fig. 5.1a, b). The cytology of pollen at the time of shedding (2 or 3 cells) has important correlations with a number of physiological features of the pollen such as viability, storage and in vitro germination. In general, 2-celled pollen show longer viability, store well and germinate on a simple medium when compared to 3-celled pollen. Also the species with 2-celled pollen show gametophytic type of self-incompatibility, whereas those with 3-celled pollen show sporophytic type of self-incompatibility. Mature pollen grains generally contain reserve nutrients in the form of starch (Fig.5.2a) or lipids. The phase of pollen, from their shedding until they land on the stigma, is termed free dispersed phase; it plays a crucial role in plant reproduction as it facilitates gene flow because of their dispersal and transport to other conspecific plants/populations through various pollinating agents.