Abstract:

The overcast, rainy, weak light or preternatural high temperature weather, which badly affects the grain weight, frequently occurs after anthesis. Previous studies have indicated that the effects of ecological factor on wheat grain weight were realized by changing the endogenous hormone contents. While little information is available on grain filling process and endogenous hormone contents under high temperature and light stress after anthesis of wheat. Therefore, effects of high temperature, shading stress and double stress of them after anthesis on grain filling process and endogenous hormone contents of wheat were investigated. Compared with CK, all stress treatments obviously reduced kernel weight and the effect of double stress of high temperature and shading at metaphase on kernel weight was the most significant. The decline of single kernel weight was mainly caused by the decrease of slight-increase period filling rate and mean filling rate, and not by filling duration, which had a little effect on kernel weight. The changes of mean filling rate, maximum filling rate, slow-increase period filling rate, fast-increase period filling rate and slight-increase period filling rate were attributed to a decrease of GA₃ or increase of ABA in the grains during grain filling. The correlations among changing rates of endogenous hormones indole-3-acetic acid (IAA), gibberellin (GA₃), zeatin riboside (ZR), and abscisic acid (ABA) as well as mean filling rate in grain were analyzed. The results showed that the grain filling rate was mainly regulated at the early grain filling stages (7 to 12 days after anthesis) and late grain filling stages(19 to 28 days after anthesis) by GA₃ and at middle grain filling stages(12 to 19 days after anthesis) by ABA. The correlation of the mean filling rate with ABA was closer than that with GA₃. No significant correlation was found between grain filling rate and the changes of ZR or IAA content during the whole grain filling period.

Key words: Wheat, High temperature, Shading, Double stress, Endogenous hormones, Grain, Filling process