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 cells^1,2. 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 mechanism^3–6. 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 mechanism^4,6–10.