The interactions of plant growth regulators and H2O2 during germination improvement of sweet corn seed through spermidine application

Low seed vigor was the main constraint on the production of sweet corn in China. Spermidine (Spd) was proved to enhance sweet corn seed germination. However, little was known about the metabolisms and interactions of plant growth regulators (PGRs) and H2O2 in the enhancement of Spd upon sweet corn seed germination. Spd, GA, C2H4 and H2O2 soaking treatments significantly enhanced seed vigor; while their respective biosynthesis inhibitors and ABA significantly declined seed vigor. Besides, as compared with control, seed vigor showed no significant difference in Spd+ProG (prohexadione-calcium, the inhibitor of GA), however it decreased significantly in Spd+ABA. The seed vigor treated by Spd+AVG (aviglycine hydrochloride, the inhibitor of C2H4) and Spd+NAC (n-acetyl-l-cysteine, a scavenger of H2O2) were significantly lower than those soaked in Spd solution, but still significantly higher than the control. Spd+NAC with significantly lower H2O2 content still up-regulated GA and C2H4 contents and down-regulated ABA content during seed germination. The results suggested that it was Spd rather than H2O2 (produced through Spd) made a direct effect on PGRs metabolism regulation in seed germination enhancement by Spd. The metabolism of GA and ABA played crucial rolesas compared with C2H4 and H2O2. Besides, complicated PGRs interactions and crosstalk between H2O2 and PGRs existed during sweet corn seed germination after Spd soaking, and ABA might be a key hormone in this process.