Abstract:Abstract: To investigate the influence and physiological mechanism of biogas slurry application on maize (Zea mays L.) seedlings under drought stress. Use ‘Xianyu 335’ (moderate drought resistance line) and ‘Zhongdan No.2’ (stronger drought resistance line) were used as materials to study the alleviating effect of biogas slurry on the effect of maize seedling growth and photosynthetic parameter under 10% PEG-6000 simulated drought stress. The results showed that compared with the control, the seedling height, stem diameter, leaf area, root length of maize hybrid line Xianyu 335 and Zhongdan No.2 decreased obviously under drought stress. Xianyu 335’ decreased by 23.8%, 10.3%, 19.2%, and 29.5% respectively, and Zhongdan No.2 decreased by 16.2%, 5%, 17.7%, and 21.7% respectively. The root activity increased by 58.2% and 71.9% respectively. and the root-top ratio increased by 36% and 26.3% respectively. The content of soluble sugar increased by 21% and 38.61% respectively, the proline content increased by 32.3% and 17.6% respectively. The content of MDA increased by 78.4% and 57.6% respectively. The activities of superoxide dismutase ( SOD), peroxidase ( POD), catalase ( CAT) increased, and Xianyu 335 increased by34.3%, 26.9%, and 39% respectively, and Zhongdan No.2 increased by 62.7%, 78.2%, and 38.2% respectively. Chlorophyll SPAD value decreased by 10.6% and 5.8% respectively. Pn, Gs, Tr, and WUE of Xianyu 335 decreased by 26.4%, 17.0%, and 16.2% respectively, while those of Zhongdan NO.2 decreased by 16.9%, 23.6%, and 23.1% respectively, on the contrary, the WUE of Zhongdan NO.2 increased by 18.7%. Applying 50% biogas slurry obviously alleviated the damage of maize seedlings caused by drought stress. Compared with PEG treatment, the seedling height, stem diameter, leaf area and root length of maize hybridization lines Xianyu 335 and Zhongdan NO.2 increased significantly, with the seedling height, stem diameter, leaf area and root length of Xianyu 335 increased by 38.7%, 28.6%, 30.6%, and 24.7% respectively, while those of Zhongdan NO.2 increased by 36.8%, 43.6%, 28.2%, and 33.2% respectively. The root activity of Xianyu 335 and Zhongdan NO.2 increased by 47.7% and 66%, respectively, and the fibrous root number increased by13.3% and 18.0%, respectively, instead, the root-top ratio decreased by 33.3% and 30.2%, respectively. The content of soluble sugar and the proline content of Xianyu 335 increased by 7.37% and 11.57%, respectively, while the content of soluble protein is unchanged, the those of Zhongdan NO.2 increased by 28.2%, 17.15%, and 14.6% respectively. The leaf dry fresh ratio increased by 50% and 25%, respectively. In leaves, MDA decreased by 36.06% and 44.6%, respectively. The activities of SOD, POD, and CAT increased further, Xianyu 335 increased by 19.3%, 20.7%, and 42.3% respectively, and Zhongdan NO.2 increased by 26.5% and 73.6%, respectively, however, its CAT activity is decreased. Chlorophyll content and photosynthetic parameters Pn, Tr, and WUE increased,and chlorophyll content increased by 10.4% and 5.8% respectively. Photosynthetic parameters Pn Tr, and WUE of Xianyu 335 increased by 47.4%, 35.3%, and 9% respectively, and Zhongdan NO.2 increased by 42.9%, 4.7%, and 36.3% respectively. The results showed that 50% biogas slurry applying concentrations could effectively improve the photosynthetic capacity of Xianyu 335 and Zhongdan No.2 seedlings under drought stress, significant increase of the activities autioxidant enzyme and the concentration of osmotic regulatory substances, and reduce the membrane permeability, so as to alleviate the drought stress, and the alleviating effect on drought stress to the Zhongdan No.2 is more significant remarkable between two lines of maize.