Activités ATPasiques du nœud cotylédonaire et du bourgeon cotylédonaire du pois inhibé, réactivé ou soumis à la fusicoccine

Abstract

The activity of enzymes which hydrolyse ATP at neutral pH was demonstrated cytochemically in the cotyledonary node and in three types of cotyledonary buds (inhibited, released from dominance, treated with fusicoccin). In the intact plant, the transfer cells of the cotyledonary node showed a very strong Mg2+-dependent, ouabaïne-insensitive ATPase activity, essentially located on the outer surface of the plasmalemma. A high concentration of K+ stimulated the ATPase activity of the plasmalemma of transfer cells and sieve elements. ATPase activity was even more specifically detected along mitochondrial cristae and the tonoplast of the phloem transfer cells and along the reticular membranes of the xylem transfer cells. All these activities which were not modified by decapitation increased after a fusicoccin treatment. In the inhibited bud the same pattern of ATPase activity occurred along the plasma membrane but with a lesser intensity. At the base of the first-bud internodes the phloem transfer cells were the only ones with a high ATPase activity. Decapitation induced, without cell specificity, an increase in the ATPase activity of the plasmalemma for the entire bud, while after fusicoccin treatment, the increase extended to the tonoplast. Proper controls eliminate the possibility of artifactual reactions or interactions with other enzymes.