Effects of spermidine on seed germination and seedling drought resistance of white clover under osmotic stress induced by PEG

The aim of this study was to investigate the effect of spermidine (Spd) on seed germination and seedling drought resistance of Trifolium repens cv. Ladino under osmotic stress induced by different concentration of polyethylene glycol 6000 (PEG-26000). The results showed that 20 μmol·L-1 Spd soaking significantly enhanced seed germination percentage and germination index under 10% and 15% PEG solution, and increased radicle length and seedling fresh weight under 15% PEG solution, whereas had no effect on dry weight. Meanwhile, when exposed to 20% PEG, seedlings treated with 20 μmol·L-1 Spd showed a higher antioxidant enzymes activities including SOD, POD, CAT and APX, and leaf RWC, and decreased the electrolyte leakage and MDA content compared to control. In conclusion, these results indicated that Spd can effectively promote the ability of seed germination and environmental adaptability of whiter clover seedlings under osmotic stress, protect the structure of cell membrane, and alleviate the oxidative damage induced by osmotic stress resulting in the improved drought tolerance of white clover.