To evaluate the effect of ethephon and GA3 on chlorophyll degradation, peroxidase activity and respiration during the postharvest senescence of broccoli (Brassica oleracea L. var. italica), harvested inflorescences of cv. Piracicaba Precoce were immersed, for one hour, in 0.1, 1.0, 10, 100 and 1000 mg.L-1 ethephon solutions. In a parallel assay, inflorescences were sprayed with 50, 250 and 1000 mg.L-1 of GA3. The experiments were set up in a complete randomized design, with three replications for ethephon application and four replications for GA3 application. The concentrations of 100 and 1000 mg.L-1 ethephon enhanced the rate of chlorophyll degradation, evident 48 hours after harvesting, while the control retained 80% of its initial chlorophyll content. Treatment with 1000 mg.L-1 ethephon increased significantly peroxidase activity and respiration 24 hours after harvesting. GA3 did not affect the degradation of chlorophyll and respiration. However, it diminished the activity of peroxidases 25%, 38%, and 43% for the treatments of 50, 250 and 1000 mg.L-1 of GA3, respectively, in relation to the control, 48 hours after harvesting. The results indicate that peroxidase activity was very sensitive to alterations after harvesting. However, this is still an infrequently used characteristic in postharvest studies. Finally, the broccoli possesses a relatively high respiration and a fast degradation rate of chlorophyll in its postharvest life, and is able to respond to ethylene from external sources.
Brassica Oleracea L. var italica; GA3; ethephon; chlorophyll; peroxidase; respiration
