Abstract: The leaf senescence is one of the main problems at filling stage in soybean grain, affecting leaf photosynthetic physiology. Previous researches have showed that chemical growth regulators have been used to delay leaf senescence, therefore, to raise grain yield. In the present study, a soybean (Glycine max) cultivar, ‘Kennong4’ with three treatments by spraying SOD simulation material (SOD_M), Choline chloride (Cc) and Diethyl aminoethyl hexanoate (DTA-6) were employed to compare differences of several endogenous hormones and protective enzyme activities in soybean leaves in a field experiment. The results show that, compared with CK, 7–15% of yield increases were obtained with SOD_M and DTA-6 treatments. IAA, GA, and CTK contents significantly increased with SOD_M treatment from the 5th to the 30th day after spraying. DTA-6 improved the contents of IAA and CTK from the 15th to the 30th day after spraying, however, the contents of IAA and CTK reduced with Cc treatment in varying degrees. On the other hand, with the time elongation after spraying PGRs, three regulators increased SOD and POD ac-tivities in soybean leaves. SOD activity in leaves with DTA-6 spraying was higher than that with SOD_M spraying, although POD activity in leaves with DTA-6 spraying was lower than that with SOD_M spraying. In addition, SODM and DTA-6 also enhanced CAT activity in soybean leaves and slowed the increase of MDA. But the effect of Cc was not obvious. The results above indi-cated that it is effective to increase seed yield or delay leaf senescence, and regulate the level of endogenous hormones and physiological function of protective enzymes by spraying SOD_M and DTA-6 on soybean leaves.

Key words: Plant growth regulator, Soybean, Endogenous hormone, Protective enzyme activity