Response of physiology and biochemistry of soybean seedling to soil water deficit and air humidity

A pot experiment was conducted to study physiological response of water deficit and air humidity changes of soybean seedlings (Glycine max) for 5day, 10day under different control treatments. The experiments included four water stress levels control group (C1), mild drought (C2), moderate drought (C3), and severe drought (C4), and three air humidity levels (35%-45%, 55%-65%, 85%-95%). The severe drought stress resulted in decreasing leaf relative water content (LRWC), incneasing of soluble sugar and free proline content, decreasing of activities of SOD, and improving of POD activity POD. With the air humidity rising, LRWC raised too, soluble sugar decreased and free proline kept osmotic potential. The decreasing content of MDA also indicated that higher air humidity could resist membrane lipid peroxidation, and the harm to soybeans growing. Soybean had some tolerance to drought stress in a short period. Increasing air humidity can weaken the soil drought damage when drought stress is not so serious.