Specific Requirement of Potassium for Light-Activated Opening of Stomata in Epidermal Strips

摘要: The effect of various ions on stomatal opening was studied in isolated epidermal strips Vicia faba L. Stomata floating 10 mm KCl and CO(2)-free air opened light, closed subsequent darkness, then fully again when illuminated. A light-activated highly specific K(-) (and Rb(+)) found. When were floated high concentrations (50 or 100 meq/liter) Li(+), Na(+) Cs(+), stomata but light had very little the required for opening. With K(+), produced dark same as with other alkali ions. Light, however, lowered more than 100-fold concentration K(+) maximal Thus only greatly accentuated by light. NH(4) (+) Mg(2+) did not produce opening.No anion is association K(+). Opening Cl(-), Br, NO(3) (-) used counter ions, less SO(4) (2-) used, particularly at higher dark.The results are discussed relation to recent proposal that basis uptake amounts sufficient act an osmotic agent. This work also demonstrates, first time, a physiological process specifically requiring Assuming ion integral part opening, guard cells would appear have mechanism degree specificity previously unknown plants.