CHANGES IN MALONDIALDEHYDE CONTENT AND IN SUPEROXIDE-DISMUTASE, CATALASE AND GLUTATHIONE-REDUCTASE ACTIVITIES IN SUNFLOWER SEEDS AS RELATEDTO DETERIORATION DURING ACCELERATED AGING

Sunflower (Helianthus annuus L.) seeds progressively lost their abilit y to germinate at 25 degrees C, the optimal temperature for germinatio n, after accelerated aging was carried out at 45 degrees C (a temperat ure too high to permit germination) in water or at 76 or 100% relative humidity (RH). The deleterious effects of the high-temperature treatm ent increased with increasing seed moisture content. Incubation of see ds at 45 degrees C in water resulted in electrolyte leakage, which ind icated a loss of membrane integrity. A relationship between leakage an d loss of seed viability could not be assumed, since no increase in el ectrolyte efflux occurred after aging at 100% RH. Accelerated aging in duced accumulation of malondialdehyde, suggesting that seed deteriorat ion was associated with lipid peroxidation. However, there was no dire ct relationship between lipid peroxidation and deterioration in membra ne integrity. Loss of seed viability was also associated with a decrea se in superoxide dismutase, catalase and glutathione reductase activit ies. Finally, the results obtained suggest that sunflower seed deterio ration during accelerated aging is closely related to a decrease in th e activities of detoxifying enzymes and to lipid peroxidation.