Role of ethylene in senescence of watercress leaves

Detached watercress leaves showed a rapid senescence rate as compared with other herbs. It was therefore of interest to investigate the role of ethylene in the rapid senescence of watercress leaves, and So estimate the efficacy of various inhibitors of elhylene synthesis (aminoethoxyvinylglycine, AVG) and action (CO₂, Ag⁺) in retarding senescence processes. The progress of senescence in watercress bunches (leaves attached to cut stems) and in detached leaves was estimated by measuring the rate of chlorophyll (Chl) loss, proteolysis and lipid oxidation. Evidence is presented showing that application of 11% CO₂ to watercress bunches in a flow-through system had a long-lasting effect on senescence, exhibited by highly efficient retardation of all the senescence processes tested. On the other hand, application of AVG (O.1 m M ) or Ag-(30 μ M ) to detached leaves affected Chl loss much more than prciteolysis. These results suggest that the senescence-retarding activity of CO₂ cannot be attributed solely to its action as an anli-ethylene agent and that not all senescence-associated processes are regulated by ethylene.