Effects of Drought Stress on Maize Root and Its Photosynthetic Physiological Characteristics at Seedling Stage

The changes of root and photosynthetic physiological characteristics under soil drought stress of two genotypic maizes at seedling were studied with a pot experiment with a rain shelter to keep off precipitation.The results showed drought stress affected maize root growth and absorbency at seedling with unconspicuous effect,but the ratio of active absorbing area to total root absorbing area trended to be higher than that of normal water treatment with 3.17% of Baidan 9 and 6.61% of Baidan 31 under drought stress.Drought stress distinctly reduced leaf photosynthetic rate and light energy use efficiency of maize at seedling.The average diurnal photosynthetic rate of Baidan 9 and Baidan 31 reduced by 29.67% and 41.86%,and their apparent quantum yield respectively declined by 0.017 mol/mol and 0.022 mol/mol.Drought stress also diminished the transpiration rate and the range of available light energy of maize at seedling.The water use efficiency of Baidan 9 under drought stress was higher than that of normal water treatment at 8:00～12:00 and in 50～2 000 μmol/(m2·s) light intensity.Synchronously,at 8:00 and 16:00～18:00 and in 50～2 000 μmol/(m2·s) light intensity,the water use efficiency of Baidan 31 was higher than that of normal water treatment.