Distribution of calcium in epidermal cell types of Mediterranean xeromorphic calcicoles

Calcium distribution in the epidermis of nine pubescent xeromorphic Mediterranean calcicoles has been studied using scanning electron microscopy and x-ray microanalysis. It has been revealed that leaf trichomes contain considerable amounts of Ca, but the main sinks of the element seem to be epidermal cells away from stomata. Ca content of stomatal guard cells was always low. Provided that trichomes of Mediterranean xeromorphic species lose their protoplasts very early during their differentiation, it is assumed that they might be involved in the Ca regulatory mechanism only during the very early stages of leaf development. In mature leaves. this role is retained by epidermal cells, away from stomata complexes.