Effects Of Salt Stress On Photosynthetic Characteristics,root Growth And Rhizosphere Microdomain Characteristics Of Muskmelon Seedlings

Hetao region of Inner Mongolia is the dominant producing area of melons.The melons produced in Inner Mongolia are melon-fragrant and sweet with good quality.In recent years,the problem of soil salinization is prominent,which seriously affects the production and quality improvement of muskmelon.Research on salt-tolerant physiological characteristics of muskmelon is of great significance to establish reasonable cultivation and management measures and efficient utilization of salinized soil in production.In this experiment,Hetao honeydew melon(),a high quality local variety in Hetao region,and Silver Emperor(),an excellent variety introduced into the region in recent years,were used as materials.The effects of different concentrations of NaCl stress{0mmol/L(CK),50mmol/L(T1),100 mmol/L(T2),150 mmol/L(T3),200 mmol/L(T4)mmol/L} on root growth,activity and membrane lipid peroxidation of two melon cultivars were investigated.Rhizosphere soil microorganisms and soil enzyme activities;The physiological characteristics of salt-tolerant seedlings of two melon varieties were preliminarily understood,which provided a basis for clarifying the salt-tolerant mechanism of melon and establishing reasonable cultivation and management measures in production.The main research results are as follows:(1)Root growth and activity of muskmelon seedlings were different under salt stress of different concentrations.Among them 7 d,low concentration of salt stress(T1,T2)under the two varieties of melon seedling root volume and root surface area are increased significantly than control,hetao melon root activity under the T1 treatment is significantly higher than control,silver emperors also keep the high level,severe root growth under salt stress(T4)was significantly inhibited,root activity was significantly lower than control.Under the stress of T3 and T4 for 14 days,the root growth,root volume and root surface area of Hetao Migua were inhibited,while the root growth of Yinhuang was significantly inhibited only under the stress of T4.(2)The content of MDA in the root system of the two muskmelon cultivars remained at a low level under low salt concentration.With the increase of salt concentration,MDA content increased and reached the maximum under T4 treatment.The activities of antioxidant enzymes in the roots of both melon varieties showed a trend of increasing at low concentration and decreasing at high concentration.The activities of antioxidant enzymes in the roots of Hetao melon and Yinking melon reached the maximum under T1 and T2 treatment,respectively.(3)The number of microorganisms in the rhizosphere soil of the two melon varieties decreased with the increase of salt concentration,and the change trend of the activities of catalase and phosphatase in the rhizosphere soil was consistent with that of the two melon varieties.The change trends of urease activity and sucrase activity in rhizosphere soil were different.On the whole,the urease activity of Hetao honeydew melon was similar to that of CK after 7 days of treatment,but it was significantly higher under low concentration(T1)treatment than that of CK,and significantly lower under high concentration(T3-T4)treatment.With the increase of treatment time,the change trend of the two varieties of muskmelon was consistent,which was significantly higher under low concentration(T1)than CK,and significantly lower under high concentration(T3-T4)than CK.During the whole treatment process,the rhizosphere soil sucrase activity of Hetao honeydew melon under T2-T4 treatment was significantly lower than that of CK,while the rhizosphere soil sucrase activity under high concentration(T3-T4)treatment for 7d was significantly lower than that of CK,and the trend of change after 14 d treatment was consistent with that of Hetao honeydew melon.(4)The net photosynthetic rate,stomatal conductance,transpiration rate and intercellular CO2 concentration of two kinds of muskmelon seedlings showed a decreasing trend with the increase of treatment concentration.Fo of Hetao melon and Silver Emperor showed an upward trend with the increase of treatment concentration,while Fm,Fv/Fm and Fv/Fo showed a downward trend with the increase of treatment concentration in the whole treatment process.(5)Based on the comprehensive analysis of root growth,root activity,membrane lipid peroxidation and leaf photosynthetic characteristics of the seedlings of the two melon varieties under salt stress,it was concluded that the seedlings of the two melon varieties had certain salt tolerance,and the salt tolerance of Yin Emperor was slightly better than that of Hetao honeydew melon.