关键词: 亚精胺, 干旱胁迫, 苜蓿, 生理指标

Abstract: In order to explore the physiological mechanism of exogenous spermidine (Spd) to improve drought resistance and drought mitigation in alfalfa (Medicago Sativa L.),'Longmu No.807’cultivated by nutrient solution was used as the experiment material and 20% polyethylene glycol (PEG-6000) was used to simulate osmotic stress. The effects of spermidine with different concentrations (0,0.3,0.6，0.9,1.2 mmol·L-1)on membrane permeability substances,antioxidant enzyme activities,contents of osmotic adjustment substances and chlorophyll were analyzed. The optimal relieve concentration of exogenous Spd was evaluated by the membership function method.The results showed that when 0.9 mmol·L^-1Spd was applied to alfalfa seedlings under 20% PEG stress,the content of MDA and H₂O₂，O^-_2· production rate decreased by 37.29%，46.84% and 39.00%,respectively. The antioxidant enzyme activities of SOD and CAT increased by 65.75% and 60.21%,respectively. The contents of soluble protein,proline and chlorophyll increased by 93.27%，52.30% and 76.54%;respectively,when 0.6 mmol·L^-1Spd was applied to alfalfa seedlings under 20% PEG stress. The activity of POD increased by 26.07%. The contents of soluble sugar increased by 77.62% when 1.2 mmol·L^-1Spd was applied. The comprehensive evaluation of subordinate function showed that suitable Spd concentration could alleviate the damage of drought to alfalfa seedlings and Spd concentration of 0.9 mmol·L^-1 was the best in the study herein. Therefore,exogenous Spd could stabilize the cell membrane system,enhance the antioxidant capacity,maintain the osmotic balance,and alleviate the damage of drought to alfalfa seedlings.

Key words: Spermidine, Drought stress, Alfalfa, Physiological indexes