Abstract: 【Objective】This study aimed to elucidate the relationship between NaCl stress and root exudates components. 【Method】 Cucumber cultivars with different NaCl tolerances were used as experimental materials. Root exudates components in the whole growth period of cucumber under different NaCl concentrations (0, 100, 200, 300 mmol NaCl•L-1) were analyzed. 【Result】Except for the 300 mmol NaCl•L-1 concentration treatment, soluble sugar content in NaCl-tolerant cucumber root exudates was higher than that in NaCl-sensitive cultivar on 50 d after cucumber transplanting. Sixteen kinds of free amino acids were detected in cucumber root exudates. The variety and contents of free amino acid were higher in NaCl-tolerant cucumber root exudates than in NaCl-sensitive cultivar at the seedlings stage. On 30 d after cucumber transplanting, total amino acid content in NaCl-sensitive cultivar under all concentrations of NaCl and in NaCl-tolerant cultivar under 100 and 200 mmol NaCl•L-1 treatments were lower than that in the control. On 50 d after transplanting, the variety and contents of free amino acid were higher than that on 30 d after transplanting; total amino acids content in NaCl-sensitive cultivar were higher than that in NaCl-tolerant cultivar under 200 and 300 mmol NaCl•L-1 treatments, whereas the trend was the contrary for other NaCl concentrations. On 70 d after transplanting, the variety and contents of free amino acid were higher than that on 30 and 50 d after transplanting, except for the 300 mmol NaCl•L-1 treatment, total amino acids content in NaCl-sensitive cultivar were higher than in NaCl-tolerant cultivar. Under the same NaCl concentration, threonine, serine and glycine contents in the NaCl-sensitive cultivar were higher than in the NaCl-tolerant cultivar, whereas cysteine content was the contrary. There were 65 kinds of compounds were detected in cucumber root exudates with GC-MS method. The variety of these compounds was higher on 30 d after transplanting than on 50 and 70 d after transplanting. The total content of these compounds was higher on 50 d after transplanting than on 30 and 70 d after transplanting. In 300 mmol NaCl•L-1 treatment, the total content of these compounds was higher in NaCl-sensitive cultivar than in NaCl-tolerant cultivar on 30, 50 and 70 d after transplanting. 【Conclusion】Soluble sugar content in cucumber root exudates was affected by NaCl concentration and cucumber growth stage. Soluble sugar content in NaCl-sensitive cultivar was higher than in NaCl-tolerant cultivar. NaCl stress increased the variety of amino acids. The variety and total content of compounds, as detected by GC-MS, had the trend to decrease with the increass of NaCl concentration and cucumber development.

Key words: cucumber, NaCl stress, root exudates, GC-MS