Abaxial epidermal strips from leaves of Paphiopedilum leeanum were analyzed via sodium cobaltinitrite staining and atomic absorption spectrophotometry for the presence and location of potassium. On a dry weight basis K content of the abaxial epidermis was found to be 103 times less than has been reported in other species, and unlike other species no localization of K+ in guard cells of open stomata could be detected via the sodium cobaltinitrite stain for potassium.Flame photometric analysis of the mesophyll indicated that it contained normal amounts of K+ (about 1.87% on a dry weight basis). Analysis showed that the K+ content of the abaxial epidermis (0.032%) was considerably less than that of the mesophyll, a situation unlike previous reports for other species in which the epidermal concentration was found to be greater than the mesophyll. A process for exclusion of K+ from the abaxial epidermis is suggested, as is the lack of involvement of K+ as the major osmoticum in the stomatal mechanism of this species.
Water Stress Reduces Ozone Injury via a Stomatal Mechanism
