Effect Of Rhamnosin On Salt Resistance Of Chinese Cabbage In Matrix Cultivation

Soil salinization is the key factor restricting the sustainable development of agriculture.Soil salinization can be divided into field soil salinization and facility soil salinization.At present,the cultivation measures of facility agriculture are not limited to the traditional soil cultivation,among which the substrate cultivation is widely used due to the characteristics of saving time,labor and fertilizer,so the phenomenon of salt damage also exists in the substrate cultivation.At present,there are various measures to improve salinized soil,among which adding exogenous chemicals to adjust the composition and properties of soil salt,improve the salt tolerance of plants,and reduce the harm of salt are also considered effective measures.Rhamolipid is a kind of anionic biological surfactant with excellent physiological and biochemical properties.It can be used in agriculture to ameliorate soil salinization and promote nutrient absorption of plants.However,rhamnolipid has been seldom used in alleviating salt stress in plants.Therefore,in this paper,rhamnolipid was used as research material,and the effects of rhamnolipid on plant growth and development and salt resistance were studied by germination test,substrate cultivation test and substrate cultivation test containing salt,so as to provide theoretical basis for the application of rhamnolipid in saline soil.The main results are as follows:1.Rhamnolipid increased the germination rate,germination potential and germination index of pakchoi seeds under salt stress.The results showed that when the concentration of Na Cl was 150 mmol/L,the germination of Chinese cabbage seeds was significantly inhibited,and the germination rate,germination potential and germination index decreased by 4.15%,7.17%and 10.77%,respectively.Both rhamnolipid soaking and culture treatments could improve the germination ability of seeds under salt stress.Among them,the germination rate of cabbage seeds after seed soaking treatment increased the most when the rhamnolipid concentration was 60 mg/L,with an increase of 35.37%,and the germination potential and germination index increased the most when the rhamnolipid concentration was 240 mg/L,with an increase of 177.27%and 102.88%respectively.At the same time,similar results were obtained in the rhamnolipid culture treatment.The germination rate,germination potential and germination index increased significantly.The optimal concentration was 60mg/L,and the increase rate was 33.59%,96.90%and 131.56%,respectively.2.Rhamnolipid can improve the nutritional quality of pakchoi and promote the absorption of nutrients.The results showed that the biomass of Pakchoi increased first and then decreased under the two treatment methods.The spraying treatment reached a significant level when the rhamnolipid concentration was 60 mg/L,and the irrigation treatment reached a significant level when the rhamnolipid concentration was 360 mg/L.Spraying rhamnolipid also promoted the accumulation of soluble sugar,reducing sugar and soluble protein.Both treatments increased the contents of P,K,Fe and Mn in Chinese cabbage leaves.In the concentration range（30～480 mg/L）,irrigation treatment increased the contents of chlorophyll a,chlorophyll b and carotenoid,while spraying treatment only promoted at low concentration（30 mg/L）.At the same time,spraying and irrigation of 240mg/L rhamnolipid significantly increased the activity of antioxidant enzyme SOD in Pakchoi leaves and plant stress resistance.3.Rhamnolipids improve the salt resistance of pakchoi.The results showed that compared with the blank control,the growth and physiological activities of pakchoi under salt stress were significantly affected,chlorophyll a decreased by 22.74%,excessive absorption of sodium ion 715.96%and chloride ion 156.40%.Leaf spraying or root irrigating rhamnolipid significantly increased the fresh and dry weights of pakchoi,and the water content of leaves.In terms of photosynthetic pigments,spraying or root irrigation with rhamnolipid significantly increased the contents of chlorophyll a,chlorophyll b and carotenoids in leaves,and the optimal treatment concentration ranged from 30 mg/L to 60mg/L;The activity of antioxidant enzymes also increased to a certain extent.In the spraying treatment,the low concentration of rhamnolipid（30 mg/L）has the best effect on improving the activity of SOD,and the high concentration of rhamnolipid（480 mg/L）has the best effect on improving the activity of POD.In the irrigation treatment,when the concentration of rhamnolipid was 480mg/L,the activities of SOD and pod were the highest,and the content of MDA was reduced.Spraying and irrigation of rhamnolipid also promoted the absorption of K⁺and Mg²⁺and inhibited the excessive absorption of Na⁺and Cl^-.Comprehensive the above results,the rhamnolipid can as organic nutrients improve the nutritional quality of pakchoi,increase the biomass,and can be used as a new added exogenous substances inducing plant resistance,improve plant salt resistance,reduce the harm of plant salt,in soil improvement,soil amelioration,substrate cultivation regulation in has certain application prospect.