Stomatal movements and ion fluxes within epidermis of Commelina communis L.

Abstract

STOMATAL movements are brought about by differential changes in turgor pressure between guard cells and other epidermal cells1,2. The mechanism by which the turgor changes occur has been investigated for well over a century and a number of hypotheses have been proposed but none has been found to be completely satisfactory. Research in recent years has provided increasing evidence that active ion transport plays a major role in the stomatal mechanism3–6. It has been shown that, as stomata open, certain ions move into the guard cells and that this ion influx may be a dominant factor in raising the guard cell osmotic concentration. As a result, water enters the guard cells and brings about the opening movement. During closure of stomata the process seems to reverse whereby ions are lost by the guard cells. Cl− and K+ seem to be the major ions involved in the stomatal mechanism4,6–10.