Summary

The now nearly routine isolation of large numbers of viable sperm cells from pollen or pollen tubes of both dicot and monocot flowering plants has opened up a new field of research in plant biology. These unique plant cells are being studied using techniques that were previously more amenable to cultured animal cells. Investigations of synthetic processes, membrane structure, transport, and fusion and recognition properties are being carried out. When the ability to isolate sperms is equaled by the ability to isolate eggs and/or embryo sacs, biologists studying flowering plants will have powerful tools to probe the molecular aspects of fertilization and early embryogenesis, and the opportunity of attempting to achieve genetic transformation during fertilization.

Introduction

The successful isolation and manipulation of sperm and egg cells of flowering plants has changed the approach to studies of fertilization and embryogenesis from a rather descriptive one to a highly experimental one. The history of flowering plant sperm cell isolation goes back to the 1920s, but there was a considerable gap between the work of Finn (1925) on isolation of sperm cells of Asclepias and that of Cass (1973) on isolation of sperms from pollen of barley for differential interference contrast (DIC) microscopy. The latter work combined DIC microscopy with transmission electron microscopy of sperms in pollen grains. The work of Russell (1984, 1985, 1986) on fertilization and sperm cell dimorphism, including isolation, in Plumbago provided further impetus to others (Dupuis et al. 1987; Matthys-Rochon et al. 1987; Mogensen et al. 1990; Russell et al. 1990; Theunis et al. 1991; Yang and Zhou 1989) to reexamine not only the morphology but also the function of sperms and to consider using them as fusion protoplasts in experimental fusions.