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 m easurements of thiobarbituric acid reactive substances (TEARS) in Chry santhemum morifolium RAM petals during senescence, that was arbitraril y divided into five stages. TEARS content was higher in petals from st age 5 (complete wilting) than in stage 1 (blooming). Non-significant d ifferences were detected in ethylene production between petals classif ied in stages 1-3 (50 +/- 4 pmol/g fresh weight/h). The activity of th e enzymes involved in hydroperoxide metabolism was determined, The act ivities of superoxide dismutase (SOD), catalase, peroxidases and ascor bate peroxidase (AP) were measured. SOD activity showed a maximum valu e at stage 3 (245 +/- 30 U/mg protein), followed by a decline. A progr essive increase in peroxidase (6-fold increase) and AP (6-fold increas e) activities was measured as a function of time, Petals in stage 1 sh owed 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 prese nted here suggest that lipid peroxidation and membrane damage are invo lved in deterioration of Chrysanthemum morifolium RAM petals. The sign ificant increase in the activity of SOD, catalase, peroxidases and AP in the initial stages of senescence, indicates that antioxidant defens es are triggered by coordinated mechanisms to control damage by aging in petals.