Abstract: In this study, a pot experiment was conducted to investigate the effect of waterlogging during the seedling stage on the growth and grain yield of summer maize. Different treatments of surface waterlogging (for 3, 5 or 7 d) and subsurface waterlogging (for 5, 10 or 15 d) were included during the 4-leaf stage of summer maize cultivar Xundan No. 20. The results showed that surface waterlogging at the seedling stage for 3 d or more and subsurface waterlogging for 15 d decreased the grain yield significantly. Compared with the CK, surface waterlogging for 3-7 d decreased maize yield by 58.8%-69.8% (P<0.05), while subsurface waterlogging for 15 d decreased maize yield by 47.8% (P<0.05). Yield reduction resulted from surface waterlogging for 3-5 d or subsurface waterlogging for 15 d was mainly due to the decline in grain number per spike, while surface waterlogging for 7 d would lead to the reduction in yield by decreasing the grain number per spike and the 1000seed weight. Regression analysis of the yield loss rates and the surface waterlogging durations indicated that effective measures should be taken to control waterlogging within 1 d at the seedling stage. The effect of waterlogging on the aboveground dry matter weight of maize varied with the type and duration of waterlogging at different developmental stages. The aboveground dry matter weight after the jointing stage was significantly reduced due to surface waterlogging (P<0.05), while subsurface waterlogging did not affect significantly the aboveground dry matter weight at the maturity stage (P>0.05). Surface waterlogging for 3-7 d also affected the distribution of aboveground dry matter weight, reducing the proportion of dry matter in corncob and the harvest index by 48.7%-64.1% (P<0.05). The results indicated that the yield loss rate increased with the prolongation of waterlogging duration and the yield loss rate due to surface waterlogging was greater than that due to subsurface waterlogging.

Key words: drought stress, soybean, carbon metabolism., flowering stage, α-naphthaleneacetic acid (NAA)