Effect of gibberellic acid, salicylic acid and paclobutrazol on oxidative stress in wheat seed under accelerated ageing

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.