Transfer Cells in the Root Epidermis of Atriplex hastata L. As a Response to Salinity: a Comparative Cytological and X-Ray Microprobe Investigation

Abstract

A cytological investigation has been made of the roots of the halophyte Atriplex hastata L. Transfer cells developed in the epidermis in response to salt treatment. They occurred only in a zone 1-3 mm behind the root apex and possessed a labyrinth only in their outer tangential walls (facing the root environment). When the epidermis was damaged, the adjacent exodermal cells then developed wall ingrowths in saline conditions. Ontogenetically this differentiation is correlated with the formation of the Casparian strip and the disintegration of the vessel contents. The X-ray microanalysis data on deep-frozen hydrated root specimens indicate that the epidermal transfer cells concentrate K⁺, and exclude Cl^-, relative to the medium. It is concluded that the epidermal transfer cells function in selective uptake of K⁺ which is subsequently transported laterally into the stele and secreted into the vessels by the xylem parenchyma cells.