Abstract: In order to explore the effect of the mixture of thidiazuron and ethephon on grainfilling characteristics and hormone changes in grains during late grain-filling stage of spring maize, two maize hybrids (‘Xianyu 335’ and ‘Xinxin 2’) were treated with thidiazuron and the mixture of thidiazuron and ethephon 25 days after anthesis, with water as control. The result showed that the mixture of thidiazuron and ethephon decreased the duration of rapid increase period and moderate increase period of grain-filling stage, increased the average filling rate and grain weight, significantly improved IAA (indole-3-acetic acid) and GA (gibberellin acid) contents in grains at late grain-filling stage, reduced the contents of ABA (abscisic acid) and CTK (cytokinin). At the same time, the ratios of IAA/ABA and GA/ABA in grain-filling stage were significantly increased, and the ratios of CTK/IAA and CTK/GA were decreased, while the ratios of CTK/ABA and GA/IAA were less affected. After the treatment of thidiazuron and ethephon mixture, the contents of ABA and CTK in grains of spring maize were negatively correlated with the rate of rapid growth of grain filling. Our results indicated that the mixture of thidiazuron and ethephon regulated the grain-filling process of spring maize mainly through influencing IAA, ABA, CTK and GA contents and their proportions in grains, and ultimately advanced maturity and improved the yield of spring maize. This study will provide theoretical and experimental basis for application of the mixture of thidiazuron and ethephon to maize production.

Key words: fluorine, exposure., environmental media, source, migration and transformation