Changes in Antioxidant Enzymes during Ageing of Onion Seeds

Onion seed viability during storage and drying declines with genotype specificity. Changes in antioxidant enzymes at different viability levels were investigated in seeds of the three onion cultivars Akg-12, Valencia and TEG-502. For this purpose, 95, 80, 60, 40 and 20% viability levels were obtained by the use of controlled deterioration treatments in seeds of each onion cultivar. Subsequently, catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD) activity measurements were conducted at these viability levels. POX activity was below detection limit in aged onion seeds. The activities of CAT and SOD decreased due to seed ageing in each cultivar. The decreases observed in CAT and SOD activities were more evident when seed viability decreased below 60% level. Moreover, a high level of correlation was found between loss of seed viability and the decreases occur in CAT and SOD activities, in seeds of each onion cultivar.