Abstract: Effects of three plant growth regulators(S0D ，Cc and DTA-6)by foliage spray on the photosynthetic characteristics in soybean (Kennong 4)were studied in a field experiment．The results showed that the photosynthetic rate and
transpiration rate were enhanced from the 5th day to the 30th day after spraying with DTA一6, thus the yield of soybean was markedly increased．However，spraying with SODM could alleviate the decrease of total chlorophyll content．Meanwhile，there was no direct correlation between the water use efficiency and stomatal conductance(Gs)in different treatments and the control．The time-course changes of Gs showed a double-trend performance in soybean ，the first peak appeared on the l0th day，and the second one on the 20th day．On the 30th clay after spraying，the changes of the water use efficiency and Gs with different treatments showed a similar trend, which was SODM>Cc> DTA一6 >CK．The above results indicated that foliage spraying of DTA一6 and SODM could regulate the photosynthetic characteristics and increase the yield in soybean．

Key words: plant growth regulator, soybean, photosynthetic characteristic, yield