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Keywords:

  •  Cuticle;
  • epidermis;
  • guard cell;
  • stomata;
  • trichome;
  • very long chain fatty acid;
  • wax

Contents

  • Summary  9

  • I.
    Introduction  10
  • II.
    Cuticle structure  10
  • III.
    Cuticular waxes  10
  • IV.
    Cell patterning in the epidermis  11
  • V.
    Stomatal development  12
  • VI.
    Stomatal development in dicotyledonous plants  12
  • VII.
    Mutants in stomatal development  14
  • VIII.
    Control of Stomatal Development  14
  • IX.
    Cuticle composition affects stomatal development  14
  • X.
    The HICHI gh Carbon dioxide gene  15
  • XI.
    Fatty acid elongases  17
  • XII.
    The cuticle: an alternative signalling medium?  17
  • XIII.
    Trichome development  18
  • XIV
    .Cuticle composition affects trichome development  19
  • XV.
    Cuticle composition affects pollen germination  20
  • XVI.
    Conclusions  20
  • Acknowledgements  21

  • References  21

Summary

Studies of Arabidopsis wax biosynthesis mutants indicate that the control of cell fate in the aerial epidermis is dependant upon the synthesis of the waxy cuticle that overlies the epidermal layer. Several cer mutants, originally isolated as wax deficient, not only affect cuticular wax composition but also exhibit large increases in stomatal numbers. Stomatal numbers are also affected in hic mutant plants, but despite HIC encoding a putative wax biosynthetic enzyme the hic phenotype of increased stomatal numbers is more subtle, and only seen at elevated CO2 concentrations. This suggests that environmental effects on stomatal number may be mediated through cuticular wax composition. Other putative wax biosynthetic genes, FDH and LCR, have effects on the number of trichomes that develop in the epidermis, indicating that trichome development may also be affected by cuticle composition. Thus signals from the cuticle may influence how trichome and stomatal numbers in the epidermis are determined. Wax components could be the developmental signalling molecules, or could be the mediating medium for such signals, stimulated by environmental cues, which affect epidermal cell fate.