ANTIOXIDANT ENZYMES AND LIPID-PEROXIDATION DURING AGING OF CHRYSANTHEMUM-MORIFOLIUM RAM PETALS

To characterize the physiological status of petals over the senescence period, the rate of leakage of electrolytes and weight were measured in Chrysanthemum morifolium RAM petals. Both a significant increase in electrolyte leakage to the external medium and a concomitant decrease of flower weight were observed. Lipid peroxidation was evaluated by measurements of thiobarbituric acid reactive substances (TEARS) in Chrysanthemum morifolium RAM petals during senescence, that was arbitrarily divided into five stages. TEARS content was higher in petals from stage 5 (complete wilting) than in stage 1 (blooming). Non-significant differences were detected in ethylene production between petals classified in stages 1-3 (50 +/- 4 pmol/g fresh weight/h). The activity of the enzymes involved in hydroperoxide metabolism was determined, The activities of superoxide dismutase (SOD), catalase, peroxidases and ascorbate peroxidase (AP) were measured. SOD activity showed a maximum value at stage 3 (245 +/- 30 U/mg protein), followed by a decline. A progressive increase in peroxidase (6-fold increase) and AP (6-fold increase) activities was measured as a function of time, Petals in stage 1 showed lower catalase activity (20.8 +/- 0.5 mu mol/min/mg protein) than petals in stages 2-5 (43 +/- 3 mu mol/min/mg protein). The data presented here suggest that lipid peroxidation and membrane damage are involved in deterioration of Chrysanthemum morifolium RAM petals. The significant increase in the activity of SOD, catalase, peroxidases and AP in the initial stages of senescence, indicates that antioxidant defenses are triggered by coordinated mechanisms to control damage by aging in petals.