PROTON PUMPS OF THE VACUOLAR MEMBRANE IN GROWING PLANT-CELLS

Plant growth results from the division, enlargement and specialization of cells. The two processes of the enlargement and the differentiatio n of cells are not spatially separated in plant tissue. We focus our a ttention here on the enlargement and elongation of cells. In most case s, growing plant cells contain a large central vacuole. The acid growt h theory is based on the space-filling function of the large vacuole. The active transport systems in the vacuolar membrane are essential fo r maintenance of high osmotic pressure and for the expansion of the va cuole. The secondary active transport systems of the vacuole for sugar s and ions are driven by the proton-motive force which is generated by the vacuolar H+-ATPase and H+-translocating inorganic pyrophosphatase . In this review, the relationship between cell elongation and these e nzymes of the vacuolar membrane is emphasized.