Isolation of mesophyll and secretory cell protoplasts of the halophyte Ceratostigma plumbaginoides (L.): a comparison of ATPase concentration and activity.

A method is described for isolating mesophyll protoplasts from leaves and secretory cell protoplasts from salt glands of the facultative halophyte, Ceratostigma plumbaginoides (L.). Rates of ATP hydrolysis in both cell types were determined, and levels in secretory cell protoplast preparations were fourfold higher than those in mesophyll protoplast preparations, based on total protein. The rate of ATP hydrolysis was sensitive to azide and vanadate, and stimulated by Triton-X-100. Additionally, immunoblot procedures using an antibody to the plasma membrane H(+)/ATPase was used to compare ATPase levels of the mesophyll and secretory cell protoplasts. Results indicate that secretory cells have a higher concentration of H(+)/ATPase than mesophyll cells, consistent with their putative function in salt glands.