Long-distance CO(2) signalling in plants.

Stomatal numbers are tightly controlled by environmental signals including light intensity and atmospheric CO(2) partial pressure. This requires control of epidermal cell development during the early phase of leaf growth and involves changes in both the density of cells on the leaf surface and the proportion of cells that adopt a stomatal fate. This paper reviews the current understanding of how stomata develop and describes recent advances that have given insights into the regulatory mechanisms involved using mutant Arabidopsis plants that implicates a role for long-chain fatty acids in cell-to-cell communication. Evidence is presented which indicates that long-distance signalling from mature to newly developing leaves forms part of the mechanism by which stomatal development responds to environmental cues. Analysis of mutant plants suggests that the plant hormones abscisic acid, ethylene and jasmonates are implicated in the long-distance signalling pathway and that the action may be mediated by reactive oxygen species.