Stomatal responses of Argenteum ? a mutant of Pisum sativum L. with readily detachable leaf epidermis

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Abstract
Epidermis is easily detached from both adaxial and abaxial surfaces of leaf four of the Argenteum mutant of Pisum sativum L. The isolated epidermis has stomata with large, easily-measured pores. Hairs and glands are absent. The density of stomata is high and contamination by mesophyll cells is low. In the light and in CO2-free air, stomata in isolated adaxial epidermis of Argenteum mutant opened maximally after 4 h incubation at 25°C. The response of stomata to light was dependent on the concentration of KCl in the incubation medium and was maximal at 50 mol m-3 KCl. Stomata did not respond to exogenous kinetin, but apertures were reduced by incubation of epidermis on solutions containing between 10-5 and 10-1 mol m-3 abscisic acid (ABA). The responses of stomata of Argenteum mutant to light, exogenous KCl, ABA and kinetin were comparable with those described previously for stomata in isolated epidermis of Commelina communis. A method for preparing viable protoplasts of guard cells from isolated epidermis of Argenteum mutant is described. The response of guard cell protoplasts to light, exogenous KCl, ABA and kinetin were similar to those of stomata in isolated epidermis except that the increase in volume of the protoplasts in response to light was maximal at a lower concentration of KCl (10 mol m-3) and that protoplasts responded more rapidly to light than stomata in isolated epidermis. The protoplasts did not respond to exogenous kinetin, but when incubated for 1 h in the light and in CO2-free air on a solution containing 10-3 mol m-3 ABA, they decreased in volume by 30%. The advantages of using epidermis from Argenteum mutant for experiments on stomatal movements are discussed.