Effect of seed priming with spermidine on boosting germination indicators and activity of some antioxidant enzymes in drought-stressed soybean seedlings

In order to evaluate the effect of priming by spermidin polyamine on increasing drought stress at germination and seedling growth stages of soybean, cv. Caspian, a factorial experiment was conducted based on completely randomized design with four replications at Sari Agricultural Sciences and Natural Resources University in 2016. The treatments were three drought stress levels (0, -2 and -4 bar) and three spermidine levels (0, 1 and 2 mM). The results showed that application of spermidine at the rate of 1 mM improved germination properties including germination maximum, germination rate, germination uniformity, times to 10, 50 and 90% germination, radicle length, seedling weight and final germination under mild drought stress (-2 bar). High dose of spermidine could not improve the tolerance to intensive stress in evaluated traits. Application of 1 mM spermidine led to increased activity of antioxidant enzymes ascorbat peroxidase, peroxidase, catalase, and amount of soluble protein in mild drought stress conditions compared to control. It was found no interaction between spermidine and drought stress for protein concentration. Generally results indicated that the pretreatment of seeds with spermidine improved tolerance to moderate drought stress through boosting germination indices and increasing activity of antioxidant enzymes in soybean seedlings.