Effects of Choline Chloride on Osmotic Adjustment Substances and Reactive Oxygen Species Metabolism of Cucumber Seedlings under Salt Stress

The experiment was carried out by a salt-sensitive cucumber variety 'Jinchun No.4' in a hydroponic system to investigate the effects of NaCl stress(75 mmol·L-1) on the plant fresh weight,contents of chlorophyll,soluble sugar and protein,the reactive oxygen species metabolism of seedling leaves and the positive effects of exogenous choline chloride(CC,0.5,1.0,1.5 mmol·L-1) pretreatment.The results indicated that:(1) Compared with the control plants,CC treatment induced the increase of soluble sugar and protein contents,the activities of peroxidase(POD) and catalase(CAT) and the decrease of O-·2 producing rate,and little change in the activity of superoxide dismutase(SOD) and the plant fresh weight.(2)NaCl treatment induced an increase on the contents of soluble sugar and protein,the content of malonaldehyde(MDA),the activities of SOD,CAT and POD,and a decrease on the content of chlorophyll and the plant fresh weight.(3)Activities of SOD,POD and CAT of salt-stressed cucumber leaves were significantly enhanced with the foliar spray of CC;While higher MDA content and O-·2 producing rate,lower chlorophyll content and the plant fresh weight of the salt-stressed cucumber plants were alleviated by the CC pretreatment.It is indicated that foliar spray of CC can mitigate cucumber seedlings' salt injury and promote itsgrowth by increasing activities of protective enzymes,protecting the integrity of membrane.