Tentoxin sensitivity of citrus: cotyledon-dependency of growth inhibition and reversibility of chlorosis

Tentoxin is a cyclic tetrapeptide, produced by the fungus Alternariaalternata, that induces chiorosis in germinating seedlings ofsome angiosperms. Since the most pronounced chiorotic effectof tentoxin is at the initial stages of germination most studieshave evaluated the effects of tentoxin on cotyledons. In thispreliminary work a unique biological system was establishedfor the study of the mechanism of tentoxin induced chiorosisin developing citrus seedlings. This system was used to comparethe effects of tentoxin on the in vitro germination of intactversus decotyle donized embryos. It is demonstrated here thatthe chlorotic effect of tentoxin is reversible and that ten-toxin blocks the ability of decotyledonized embryos to utilizenutrients from the growth medium and, there fore, to compensatefor the lack of cotyledons. The citrus system offers a uniqueway to study the relation between the effect of tentoxin onthe activity of choloplast ATPase and the induction of chlorosis. Key words: Tentoxin, citrus, chiorosis