关键词: 紫花苜蓿, 纳米氧化锌, 干旱胁迫, 萌发, 生长, 生理特性

Abstract: In order to clarify the promoting effect of zinc oxide nanoparticles（ ZnO NPs ）on seed germination and seedling growth of alfalfa under drought stress，Zhongmu No. 1 was used as the test material，and 10% PEG6000 solution was used to simulate drought stress. The effects of foliar spraying of different concentrations（ 0，5，10，20，50，100，200 mg/L） of ZnO NPs on seed germination and seedling growth were studied. The optimal concentration of ZnO NPs was used for seedling spraying test，and the effect of spraying ZnO NPs on the growth and physiological characteristics of alfalfa seedlings under drought stress was studied. The results showed that drought stress inhibited seed germination and seedling growth of alfalfa. Spraying ZnO NPs could promote the germination of alfalfa seeds under drought stress，the effect of 50 mg/L ZnO NPs was the best，and the germination rate，germination potential，germination index，vigor index，root length and fresh weight of seeds significantly increased by 73.91%，128.57%，108.25%，203.06%，45.54% and 60.81%，respectively，compared with drought stress treatment. Spraying ZnO NPs could alleviate the inhibition of drought stress on the growth of alfalfa seedlings，and 20 mg/L ZnO NPs had the best effect. Spraying 20 mg/L ZnO NPs on alfalfa seedlings showed that compared with drought stress treatment，the plant height，stem diameter，leaf area and aboveground fresh weight of seedlings treated with 20 mg/L ZnO NPs under drought stress significantly increased by 9.48%，30.53%，5.98% and 43.78%，respectively；the contents of chlorophyll a，chlorophyll b，total chlorophyll and carotenoid significantly increased by 21.14%，21.71%，23.66% and 24.00%，respectively；the relative conductivity and malondialdehyde（MDA）content decreased by 9.17%（p≥0.05） and 26. 22%（p<0.05），respectively；the contents of hydrogen peroxide（H_₂O_₂）and superoxide anion（O2·-）significantly decreased by 14. 38% and 14.11%，respectively；the activities of superoxide dismutase（SOD），peroxidase（POD），catalase（CAT），and ascorbic peroxidase（APX）significantly increased by 16.77%，8.12%，8.90%，and 23.70%，respectively；the proline content significantly increased by 13. 08%，while the soluble sugar content significantly decreased by 16.48%. In summary，ZnO NPs can effectively enhance plant tolerance to drought stress by improving the photosynthesis，antioxidant capacity，and osmotic regulation of alfalfa.

Key words: Alfalfa, Zinc oxide nanoparticles, Drought stress, Germination, Growth, Physiological characteristics