| Abstract: | There are two H+-pumping enzymes at the tonoplast membrane of plant vacuoles, the V-ATPase and the V-PPase. One attempt to explain the enigma of “two H+ pumps, one membrane” was the suggestion that the V-PPase has special functions in young developing and growing tissues in utilization of pyrophosphate produced in particularly active metabolism and in pumping of K+ for vacuolization. This should lead to reciprocal expression of both enzymes with time during development. Here we used stimulation of Kalanchoë blossfeldiana Poellnitz cv. Tom Thumb plants by short-day treatments to induce crassulacean acid metabolism and flowering and of Ricinus communis L. stem tissue by infection with Agrobacterium tumefaciens strain C58 to induce vigorous growth of tumours, and we compared these stimulated tissues with leaves of non-stimulated long-day controls and non-infected stem tissue, respectively. Activities and protein levels of both enzymes increased (K. blossfeldiana) or remained high (R. communis) in the stimulated tissues and decreased in the non-stimulated tissues with time. Time-dependent patterns of the two enzymes were concordant in all of the four cases and not inverse, i.e. two plants with two different conditions each, leading to very different developmental situations. |
