SEARCH

SEARCH BY CITATION

Contents

  • Summary  000

  • I.
    Introduction  000
  • II.
    Ion gradients and flux patterns  000
  • III.
    Oscillations  000
  • IV.
    The need for a Ca2+ store  000
  • V.
    Intracellular targets for Ion activity  000
  • VI.
    Extracellular targets for ions: the cell wall  000
  • VII.
    Ions in navigation  000
  • VIII.
    Role of ions in self-incompatibility  000
  • IX.
    The plasma membrane; site of global coordination and control  000
  • X.
    A model for pollen tube growth  000
  • IX.
    Conclusions  000
  • Acknowledgements  000

  • References  000

Summary

Pollen tube growth attracts our attention as a model system for studying cell elongation in plants. The process is fast, it is confined to the tip of the tube, and it is crucial for sexual reproduction in plants. In the enclosed review we focus on the control of pollen tube growth, giving special attention to the role of ions, especially calcium and protons. During the last decade technical advances have made it possible to detect localized intracellular gradients, and extracellular fluxes of calcium and protons in the apical domain. Other ions, notably potassium and chloride, are also receiving attention. An important development has been the realization that pollen tube growth oscillates in rate; in addition, the ion gradients and fluxes oscillate in magnitude. Although all the ionic oscillations show the same period as that of the growth rate, with the exception of extracellular chloride efflux, they are not in phase with growth. Considerable effort is devoted to the elucidation of these different phase relationships, with the view that a hierarchical order may provide clues about those events that are primary vs. secondary in growth control. Attention is also given to the targets for the ions, for example, the secretory system, the cytoskeleton, the cell wall, in an attempt to provide a global understanding of pollen tube growth.