MOVEMENTS OF ABAXIAL AND ADAXIAL STOMATA

Abstract

SummaryA comparative study was made of diurnal movements, and responses to a range of light intensities, of abaxial and adaxial stomata on normal and inverted leaves of Stachytarpheta indica by microscopic examination of epidermal strips fixed in absolute ethanol. Additional observations were made on Coreopsis grandifiora, Crotalaria retusa and Tridax procumbens. The natural diurnal movements in the field and light‐induced opening in the laboratory and accompanied changes in concentrations of starch and potassium in the guard cells were all substantially more pronounced in the shaded abaxial stomata than in the exposed adaxial stomata on normal leaves. The effect of leaf inversion was to accentuate these differences considerably. Carbon dioxide‐free air was not effective in overcoming the differences in opening ability of abaxial and adaxial stomata. The differential behaviour of abaxial and adaxial stomata is related, to a great extent, to differential changes in concentrations of starch and potassium in abaxial and adaxial guard cells. The greater photosensitivity of abaxial stomata is a widespread phenomenon occurring in both monocotyledons and dicotyledons irrespective of differences in stomatal density; the adaptive significance of this phenomenon is briefly mentioned.