Soybean (Glycine max L. cv Enrei) seeds were sterilized with 2% sodium hypochlorite solution and then thoroughly rinsed in water. The sterilized seeds were sown 4 cm inside surface of sand in 450 mL of quartz seedling cases wetted with 150 mL water and grown at 25°C and 70% humidity in a growth chamber (Sanyo, Tokyo, Japan) under white fluorescent light (160 μmol m-2 s-1, 16 h light period/day). Two-day-old soybeans were flooded for 2 days and hypocotyl samples were collected at the day of removal of flooding and then at 2 more points during the 4-day recovery period.