Summary

Pollen tube growth is the result of rapid polar extension of a single cell and is fundamentally different from the standard model of cellular growth in plants. The pollen tube emerges from the germpore, penetrates the stigma, and grows within the intercellular matrix of the style. As the pollen tube elongates, the living cytoplasm is confined within the tip of the pollen tube, isolated by callose plugs. The process concludes when the tube tip reaches the micropyle and discharges the sperm nuclei into the embryo sac. This chapter reviews the information available concerning the genetic control of these processes, the role of the pistil in supporting and modulating pollen function, and the genetic basis of the interaction between pollen and pistil. As well, since a positive correlation between pollen and sporophytic responses to certain traits has been demonstrated in many systems, the use of pollen assays and pollen selection for the identification of plants with desirable traits is discussed. These technologies, when integrated into the conventional breeding program, form powerful breeding tools.

Introduction

The male gametophyte has a very short life-span in the biological cycle of higher plants. Nevertheless, it is able to exist as a free organism and to express a large portion of the plant genome, including many specific genes. These genes control the development and function of a highly specialized structure, the pollen tube, which can grow at a very fast rate and respond to a sophisticated cell-cell communication system. Pollen tube growth is a unique model of plant cell growth, which more resembles fungal growth than the cell growth in a higher organism.