EFFECTS OF ETHREL ON PEROXIDASE OF ICEBERG LETTUCE LEAF TISSUE

The effect of ethrel (0.1-1.0 mM) on the development of both peroxidas e activity and brown spots in 56-day old lettuce leaves was studied. T he results showed that ethrel reduces both soluble and cell wall-bound peroxidase activity in lettuce leaves, the effect being independent o f the incubation medium pH, the ethylene-releasing ability of ethrel t herefore being not limiting. At the same time, brown spots appeared in lettuce leaves only after incubation at high concentration (1.0 mM). These results suggest that the ethrel treatments that led to the devel opment of brown spots were not related with the effect of ethrel in in ducing peroxidase, thus ruling out any key control of peroxidase in th e development of ethylene-induced brown spots.