| A study was conducted on the effects of water stress and re-watering on photosynthesis and biomass of soybean (Qin Dou NO.8) under different soil water treatments during the stages of seedling, blooming and pod-setting. The low-grade (55%～65%) and middle-grade (45%～55%) water stress was controlled respectively at blooming stage, with relative soil water content of 65%～75% from seedling to early blooming stage. The results showed that Pn
, Tr, Ci and Gs declined extremely with the stress increasing, and reduced respectively by 13.16%, 28.60%, 7.64% and 49.51% under middle-grade stress compared with CK (65%～75%), while Ls and T1 improved by 48.07% and 0.36% separately. When soil water content was remained at 65%～75% from seedling to blooming stage, and low-grade and middle-grade water stress was controlled respectively
at pod-setting stage, Pn, Tr, Ci and Gs decreased compared with CK (65%～75%), while Ls and T1 increased. When soil water was remained at 55%～65% from seedling to the early blooming stage, and the middle-grade water stress was controlled at blooming or pod-setting stage, the results showed that Pn, Tr, Ci and Gs decreased, but Ls, T1 increased compared with CK (55%～65%); while soil water was turned to 65%～75% at blooming or pod-setting stage, the photosynthesis parameters above showed adverse situation compared with middle-grade water stress treatments. When soil water content was remained at 45%～55% from seedling to the early blooming stage, and soil water was remained at 65%～75% or low-grade water stress was controlled in blooming or pod fil
ling stage, the results showed that Pn, Tr, Ci and Gs improved compared with CK (45%～55%), but Ls and T1 decreased. When the relative soil water
content from seedling to end of pod-setting stage was 65%～75%, 55%～65% and 45%～55%, respectively, Pn, Tr, Ci and Gs showed a declining trend with the soil water content decreased, while Ls, T1 showed an ascendant trend. The difference of plant biomass between middle-grade and low-grade water stress treatments was less than that between normal water treatment and low-grade wate
r stress. |