Pollination and fertilization in higher plants

Summary

Introduction

This paper focuses on events post-pollination, and will only describe the forms of pollen, stigma, style, ovary, and embryo sac where structure is relevant to the process being discussed. Data have been included on a selective basis; the paper, therefore, must not be regarded as an exhaustive analysis. For further information, a number of reviews have recently appeared relating to pollination and fertilization. These include reviews of the male gametophyte (Mascarenhas, 1989), pollen, pistil and reproductive function (Knox & Williams, 1986), pollen germination and tube growth (Heslop-Harrison, 1987; Steer & Steer, 1989), micro- and megasporogenesis and fertilization (Fougere-Rifot, 1987), the cytological basis of the plastid inheritance in angiosperms (Hagemann & Schroder, 1989), and molecular aspects of fertilization (Cornish, Anderson & Clarke, 1988). Self-incompatibility has also been deliberately given a low priority in this paper because excellent reviews have been published (Gibbs, 1986; Heslop-Harrison, 1983; Clarke et al., 1989) and in order to emphasize other aspects of the process of fertilization and its control. Where relevant in any discussion, self-incompatibility is briefly considered.

The pollen–stigma interaction

Stigma receptivity

The development of receptivity of the stigmatic surface may vary widely between species from several days prior to anthesis to several days after the flower opens (Palser, Rouse & Williams, 1989). In ‘wet’ stigmas receptivity often coincides with accumulation of stigmatic secretion and in most stigmas with a positive response for non-specific esterase (Heslop-Harrison and Shivanna, 1977).