Introduction

It is a truism of biology that most of the key processes typifying the living state in eukaryotic cells involve intracellular movement. Growth, morphogenesis, division, secretion, interaction with other cells, all require continuous physical redistribution of cell components, whether of organelles, membranes, vesicles, nuclei or chromosomes: in this respect the motility systems of the cell may be said to lie near to the heart of eukaryotic physiology. Our purpose in this outline review is to summarise some features of the life of the male gametophyte generation of the flowering plants as seen from this point of view.

Overt vectorial movement in the pollen tube itself is expressed in three main ways: in the circulation along its length of organelles and other cytoplasmic inclusions; in the net movement away from the parent pollen grain of the vegetative nucleus, the generative cell and the sperms formed from it; and in the transport and release through the plasmalemma of secretory vesicles concerned with the insertion of precursor materials into the growing wall and the release of enzymes into the environment. All of these processes are conducted within the confines of a single tip-growing, partly heterotrophic, cylindrical cell.

It is well established for both plant and animal cells that intracellular motility depends on interaction with cytoskeletal elements. Two systems are positively known from the pollen tube: one micro tubule based, and the other actin-fibril based.