ATP-DEPENDENT AND NADH-DEPENDENT MEMBRANE-POTENTIAL GENERATION IN PLASMALEMMA ENRICHED VESICLES FROM PARENCHYMA OF DORMANT AND NONDORMANT JERUSALEM-ARTICHOKE TUBERS

Using a membrane potential probe, Oxonol VI, it was possible to demons trate generation of ATP- and NADH-dependent membrane potential across the plasmalemma, with membrane vesicles derived from parenchyma cells of Jerusalem artichoke tubers (Helianthus tuberosus L.). It was shown that ATP- and NADH-dependent membrane potential generation was higher in dormant material than in non-dormant tissue and that the effects of ATP and NADH on membrane potential generation were additive. ATP-depe ndent potential generation was sensitive to vanadate, an inhibitor of plasmalemma ATPase activity. The results are discussed in relation to the properties of the different enzymes bound to the plasma membrane. the morphogenetic potentialities of tuber buds and the hypothesis that tuber dormancy could be an extreme case of nutrient deficiency induce d by short-distance intercellular relationships.