Abstract

Seed ageing during storage is a complex biochemical and physiological process that can lead to reduce seed germination. This phenomenon was associated with increasing of total antioxidant activity during ageing. To study the effects of hormones on seed ageing, aged wheat seeds (control, 90 and 80% viabilities) were treated with GA3, salicylic acid and paclobutrazol and antioxidant system was investigated as molecular biomarkers for seed vigour. The results showed that seed priming treatment significantly affected germination percentage, normality seedling percentage, H2O2, MDA, CAT, APX and GPX activities. Maximum germination percentage was achieved in GA3 priming in control treatment. Germination percentage and normal seedling percentage increased in other GA3 priming treatment compared with other hormones. Also ageing increased MDA and H2O2 content. MDA was considered sensitive marker commonly used for assessing membrane lipid peroxidation and H2O2 resulted in toxicity to cellular membrane system and damages to plant cells. Amount of H2O2 and MDA declined in GA3 treatment. CAT, GPX and APX activities were reduced by increasing the ageing time and at different levels of priming. The highest APX activity was observed in salicylic acid control treatment and the highest GPX and CAT activities were obtained in GA3 control treatment. The lowest MDA and H2O2 were shown in GA3 control treatment, too. Hormone priming increased antioxidant enzyme activity and decreased amount of reactive oxygen space and malondialdehyde (MDA) under ageing treatment. Also, GA3 priming treatment had a significant effect on germination percentage and number of normal seedlings. Generally, ageing seed increased ROS and lipid peroxidation. Antioxidant enzymes activity of aged seeds increased after hormone priming.