XVI International Botanical Congess

To examine whether ethylene - induced cell death is cell cycle -dependent, the tobacco, TBY-2 cell line was blocked at G1/S-phase with aphidicolin, exposed to ethylene (17.7 ml l-1 in the head-space above the liquid medium) 3.5 h later, and then at hourly intervals. Ethylene was also added at the same times to medium supplemented with silver nitrate (1.2 mM), known to inhibit ethylene action. Within 0.5 h of the first injection (early G2), mortality detected by a dual staining technique, increased to 9 % cf. 3% in the controls. Subsequent peaks were detected in M/G1 (17%) and in the following early G2 (14%) and M/G1 (7%). Smaller peaks were also detected at these times in the silver treatment. Hence cell cycle sensitivity to ethylene, partly ameliorated by silver ions, was evident. Data showing the extent to which programmed cell death is a feature of these responses, will be presented.