Effects Of Chito-oligosaccharides On Growth Physiology And Yield Quality Of Cabbage Under Salt Stress

Suitable soil environment is the guarantee of the growth and development of cabbage（Brassica oleracea var.capitata L.）.Salinized soil seriously affects the growth and development,yield and leaf quality of cabbage,and reduces the economic benefits of cabbage;Chitooligosaccharide（COS）has the functions of regulating plant growth and development,activating plant defense responses,etc.,The research on chito-oligosaccharide has been reported in other horticultural crops,and the use of chito-oligosaccharide in the salt resistance of cabbage is not common,so it is of great significance to study the effect of chito-oligosaccharide on the salt tolerance of cabbage.In this experiment,the cabbage variety’Fulü’was used as the material,and the leaves of its seedlings were sprayed with different concentrations(0,25,50,75,100,125 mg·L^-1)of chito-oligosaccharide（COS）solution was sprayed to determine the growth indexes such as root length,plant height and stem thickness,at the seedling stage under salt stress,and Physiological indexes such as relative conductivity,soluble sugar content,antioxidant enzyme activity.Meanwhile The effects of chito-oligosaccharides on the growth,physiological characteristics,yield and quality of cabbage at seedling stage under salt stress were studied,and the optimal treatment concentration was selected in order to improve the salt resistance of cabbage and provide a theoretical basis for cabbage production.The results are as follows:1.Under salt stress,after treatment with different concentrations of chito-oligosaccharides,the plant height,stem thickness,root length,dry quality,fresh quality,daily average dry weight growth（G value）,root-to-head ratio,leaf area and strong seedling index of cabbage seedlings were significantly increased,and the optimal values increased by10.44%,23.86%,18.01%,19.0%,27.74%,14.58%,18.52%,49.26%and 14.58%compared with CK,respectively.It can be seen that different concentrations of chito-oligosaccharide treatment can significantly improve the growth index of cabbage seedlings,promote the growth of cabbage seedlings under salt stress,and alleviate the damage caused by salt stress.Comprehensive comparison of each treatment concentrations,with 100 mg·L^-1chito-oligosaccharide treatment is optimal.2.Under salt stress,after different concentrations of chito-oligosaccharide treatment,the root viability of cabbage seedlings was significantly increased,which increased by134.25%compared with CK,while the relative conductivity was significantly reduced.The chlorophyll content,transpiration rate（Tr）,net photosynthetic rate（Pn）,and stomatal conductance（Gs）increased significantly,which increased by 217.89%,479.46%,124.49%and 230.58%compared with CK,respectively,while the intercellular CO₂concentration（Ci）decreased significantly.The content of osmoregulatory substances such as soluble sugar,soluble protein and free proline was significantly increased.The activity of antioxidant enzymes such as superoxide dismutase（SOD）,peroxidase（POD）and catalase（CAT）was significantly increased,while the content of malondialdehyde（MDA）was significantly reduced.It can be concluded that the appropriate concentration of chito-oligosaccharide can effectively increase the content of osmomodulators of cabbage,antioxidant enzyme activity,enhance its photosynthetic ability and root growth ability,alleviate salt damage,ensure normal metabolism of cabbage,and using 100 mg·L^-1works best.3.Under salt stress,different concentrations of chito-oligosaccharide treatment significantly increased the plant height,plant width,outer leaf number,leaf bulb cross diameter,leaf bulb longitudinal diameter,leaf bulb compactness and single ball weight,among which,the single ball weight increased by 37.65%compared with CK.The soluble sugar,soluble protein,vitamin C and organic acid content of cabbage leaf bulb were increased by 12.66%,13.66%,14.89%and 16.44%compared with CK,respectively,while the central column length and the relative length of the central column of cabbage leaf bulb were decreased.It is concluded that the appropriate concentration of chito-oligosaccharide can significantly increase the yield of adult leaf bulbs under salt stress,improve the quality of cabbage leaf bulbs,and the comprehensive treatment effect of each concentrations shows that 100 mg·L^-1works best.