CORRELATION BETWEEN ORNITHINE DECARBOXYLASE AND PUTRESCINE IN TOMATO PLANTS INFECTED BY CITRUS-EXOCORTIS VIROID OR TREATED WITH ETHEPHON

We have investigated the arginine decarboxylase (ADC, EC 4.1.1.19) and ornithine decarboxylase (ODC, EC 4.1.1.17) activities and the levels of conjugated polyamines to explain the decrease of free putrescine le vel caused by citrus exocortis viroid (CEVd) and ethephon treatment in tomato (Lycopersicon esculentum Mill. cv Rutgers) plants (J.M. Belles , J. Carbonell, V. Conejero [1991] Plant Physiol 96: 1053-1059). This decrease correlates with a decrease in ODC activity in CEVd-infected o r ethephon-treated plants; ADC activity was not altered. CEVd infectio n had no effect on polyamine conjugates; and ethephon produced a decre ase in putrescine conjugates. Interference with ethylene action by sil ver ions prevented the decrease in ODC activity and in free and conjug ated putrescine. It is suggested that changes in putrescine level afte r CEVd infection and ethephon treatment are regulated via ODC activity and that conjugation is not involved.