Effects of Plant Growth Regulators on Seed Filling, Endogenous Hormone Contents and Maize Production in Semiarid Regions

In this study, we determined whether the application of uniconazole alone or combined with ethephon could enhance the seed-filling rates in maize by regulating the endogenous hormone contents. Uniconazole was applied to the foliage at concentrations of 0 (CK), 25 (U25), 50 (U50) and 75 (U75) mg L−1 at the 12-leaf stage. In addition, uniconazole was applied to the foliage at the 12-leaf stage and ethephon at 10 days after silking stage at concentrations of 0 (CK), 25 mg L−1 uniconazole + 100 mg L−1 ethephon (U25 + E100), 50 mg L−1 uniconazole + 200 mg L−1 ethephon (U50 + E200) and 75 mg L−1 uniconazole + 300 mg L−1 ethephon (U75 + E300). Uniconazole applied alone or in combination with ethephon significantly improved ear characters and grain yield. Uniconazole applied alone or combination with ethephon significantly improved the dry matter accumulation in seeds and seed-filling rates. Uniconazole significantly increased the abscisic acid (ABA) and zeatin (Z) + zeatin riboside (ZR) contents of seeds, but reduced the gibberellic acid (GA) contents. The application of uniconazole combined with ethephon decreased the ABA, Z + ZR and GA contents in seeds. The ABA and Z + ZR contents were significantly positively correlated, whereas the GA content was negatively correlated with the maximum seed weight, maximum seed-filling rate and mean seed-filling rate. The application of uniconazole alone significantly improved the seed-filling rates in maize by regulating the endogenous hormone contents. Thus, we conclude that uniconazole application at 50 mg L−1 in the 12-leaf stage can enhance the maize production.