lipid peroxidation and antioxidant enzymes activity under natural and accelerated aging in safflower (carthamus tinctorius l.) seed

an experiment was conducted to determine the aging mechanism in safflower seed using natural aging treatment (storing seed at room temperature for six years) and accelerated aging ( incubating the seed at 41?c and close to 100% relative humidity for 4 ,8 and 12 days). the results indicated that both natural and accelerated aging reduced germination percentage, seed vigor and activity of catalase (cat), peroxidase (pox) and ascorbat peroxidase (apx). the results also show that malondialdhyde (mda) content, electrolyte leakage and mean time to germination (mtg) enhanced under natural and accelerated aging. the germination percentage in accelerated aging (from 94 percent in control) reached 64, 5 and 41 percent within 4, 8 and 12 days of treatment respectively. the increase in mtg was higher in natural aging than in accelerating aging. the decrease in ascorbat peroxidase activity in the aging treatments were higher than those in catalase and proxidase activities. decrease in antioxidant enzyme activity resulted in enhanced reactive oxygen species (ros) and lipid peroxidation. lipid peroxidation and membrane damage resulted to decrease seed germination and vigor. a high correlation was obtained between mda content and germination as well as seed vigor in both accelerated and natural aging suggesting that lipid peroxidation plays an important role in safflower seed deterioration in natural and as well in accelerated aging.