Effect of polyamines on germination, expression of some genes and activity of antioxidant enzymes in barley seeds with low vigour

In order to investigate the effects of seed aging and application of polyamines on the germination indices, gene expression and antioxidant enzymes activity in barley, a factorial experiment conducted based on completely randomized design with three replications. Treatments consisted of three aging levels (0, 11 and 14 days) and polyamines (putrescine and spermine). Germination indices, activity of antioxidant enzymes and expression of some genes were studied. Results showed that aging decreased germination percentage (GP) about 24 % in comparison to the control, but putrescine application increased GP about 18%. Germination rate (GR) decreased in the seeds aged for 14 days about 36 % and spermine increased GR about 87.5 %. Plumule and radicle dry weight increased 2 and 3 folds, respectively in putrescine and non-aged treatment rather than control. The highest activity of ascorbate peroxidase, peroxidase, polyphenol oxidase and superoxide dismutase (SOD) observed in the seeds aged over 14 days with putrescine application. Relative expression of genes encoding SOD and glutathione transferase was 8 and 22 folds greater, respectively in putrescine applied seeds aged for 14 days over control. Relative expression rate for HSP90 and PR10 genes was 5 and 8 folds greater than control, respectively in the same treatment. In conclusion, putrescine application invigorated the weak barley seeds and it can be related to improving the oxidative state of cells, greater protein conservation by high activity of HSP90 and increasing in the endogenous levels of seed hormones. Further in depth studies require to prove the role of hormones in seed vigor.