| Abstract: | The effects of KCI concentration in the incubation medium onstomatal opening and starch and malate metabolism in isolatedabaxial and adaxial epidermis of Commelina communis were investigated.Increasing KCI produced progressively wide apertures, reducedstarch hydrolysis and malate synthesis, but failed to eliminatethe normal disparity in abaxial and adaxial opening. The fusicoccin-stimulatedwide opening was accompanied by a dramatic enhancement of malateformation and starch hydrolysis at zero KCI, but not at 200mol m3 KCI, indicating a controlling influence of KCIconcentration on carbohydrate and malate metabolism. Accordingly,malate and Cl appear to compete for K+, and the one assumesan increasingly decisive role as the other becomes limiting.However, starch hydrolysis and malate production must play acentral role in stomatal opening in intact leaves because theyare unlikely to have such high Cl regimes as 200 molm3, though not necessarily in isolated epidermis incubatedin media enriched with inorganic ions. The restricted adaxial opening is attributed to limited K+ accumulation,starch hydrolysis and malate production in the guard cells,but the primary cause is not known. Key words: Stomata, Abaxial/Adaxial Epidermis |
