Ecophysiological studies on the drought resistance of soybean [Glycine max], 2: Effect of soil water deficit on leaf wilting and changes in photosynthesis and bleeding influenced by re-watering

The influence of non-watering and re-watering treatment to leaf wilting, photosynthesis, root respiration and bleeding in three cultivars (cv. Hwangkeumkong, Danyeobkong and Enrei) were investigated under glasshouse conditions in 1991 and 1992. Leaf wilting was first observed at the lower leaves of the main stem by suspending the water supply then later observed at the upper leaves. Conversely, the recovery from leaf wilting was started from the upper leaves to the lower leaves during the initial 3 hours after re-watering. In the process of soil drying, dead-leaf was observed successively from the lowest to the top leaf on main stem corresponding to soil moisture ranged pF 3.5-4.2. Recovering speed of the photosynthetic rate by re-watering seemed to be owned the both: high rate of root respiration and low ratio of leaf area/root weight. The bleeding from basal stem of each cultivar was constant rate for 2 hours after cutting the stem. It was also confirmed that the bleeding rate was significantly correlated with root respiration