Effects Of Different Alkaline Salt Treatments On The Physiological And Biochemical Characteristics Of Saposhnikovia Divaricata(Turcz.)Schischk.and The Quality Of Its Medicinal Materials

Saposhnikova divaricata（Turcz.）Schischk.is a perennial herbaceous plant in the Umbelliferae family,used as medicine with unbranched dry roots.Our research group found in the collection of germplasm resources for S.divaricata that a large number of wild S.divaricata are naturally distributed on soda saline alkali land.However,there is currently little research on the growth and physiological characteristics of S.divaricata under different alkaline salt environment conditions,and the growth adaptability on soda saline alkali land is still unclear.Therefore,this article uses different ratios and concentrations of alkaline salts to treat S.divaricata,and synthesizes three levels of S.divaricata growth characteristics（seed germination,seedling growth,growth status）,physiological regulatory mechanisms（antioxidant enzyme system regulation,osmotic regulation,inorganic ion absorption and transportation,photosynthetic physiological regulation）,and secondary metabolites such as Cimicifuga glycoside,Cimicifuga glycoside,5-O-methylvisualitol glycoside,and Helmingin glycoside,Exploring the tolerance threshold and salt tolerance mechanism of S.divaricata in soda saline alkali soil,providing scientific basis for efficient utilization of soda saline alkali soil during S.divaricata planting process.The main research findings are as follows:1.The effect of different alkaline salt treatments on the germination and seedling growth of S.divaricata seeds.At a concentration of Na HCO₃:Na₂CO₃=1:0 and 5 g/L,the germination rate reached the highest,increasing by 29.17%compared to CK.Appropriate alkaline salt treatment has a promoting effect on the germination of S.divaricata seeds;During the growth process of seedlings,different alkaline salts have a greater inhibitory effect on the root of S.divaricata than on the embryo.According to the establishment of a regression analysis equation based on the relative germination rate,it can be concluded that the salt tolerance thresholds of S.divaricata seeds under four different ratios of alkaline salt treatment are 17.09,16.39,12.04,and 8.09 g/L,respectively.The higher the proportion of Na₂CO₃,the stronger the inhibitory effect on S.divaricata seed germination.2.The effect of different alkaline salt treatments on the physiological indicators of S.divaricata seedlings.As the concentration of alkaline salt and the proportion of Na₂CO₃ increase,the antioxidant enzyme CAT activity and osmoregulation substances（soluble protein,soluble sugar,proline）in S.divaricata significantly increase,while soluble sugar and proline show a downward trend at20 g/L.This indicates that as the concentration of alkaline salt and the proportion of Na₂CO₃increase,S.divaricata seedlings activate antioxidant defense mechanisms to enhance the scavenging ability of reactive oxygen species and reduce the damage of reactive oxygen species to membrane lipids,When the concentration of alkaline salts reaches 20 g/L,the synthesis of soluble sugars and proline in S.divaricata is hindered,and plant life activities are inhibited.3.The effect of different alkaline salt treatments on the growth of S.divaricata and the quality of medicinal herbs.As the proportion of Na₂CO₃ and the concentration of alkaline salts increase,the number of leaf growth of S.divaricata reaches its peak at 5 g/kg,while the number of lateral roots,fresh and dry weight of roots gradually decrease.This indicates that as the concentration of alkaline salts in the soil increases,the inhibitory effect on S.divaricata growth becomes stronger.However,a concentration of 5 g/kg can promote the development of S.divaricata leaves.The root drying rate is the highest under the treatment of Na HCO₃:Na₂CO₃=1:0 and 15 g/kg,reaching 42.35%,indicating that appropriate alkaline salt treatment will promote the accumulation of dry matter in S.divaricata.As the concentration of alkaline salts and the proportion of Na₂CO₃ increase,it is beneficial for the accumulation of secondary metabolites of S.divaricata,such as Cimicifuga glycoside,Cimicifuga glycoside,and Haimao phenolic glycoside,but not conducive to the accumulation of 5-O-methylvisaminide.The ratio of5-O-methylvisamitoside to cimetin glycoside significantly decreased,with a minimum of 1.44.Due to the relative content of 5-O-methylvisamitoside being much higher than the content of the other three secondary metabolites,the total amount of the four secondary metabolites decreased as the proportion of Na₂CO₃ increased.4.The effects of different alkaline salt treatments on the physiology of S.divaricata.Different alkaline salt treatments can stimulate an increase in chlorophyll content in S.divaricata.leaves to a certain extent,and under low concentration conditions,the net photosynthetic rate（Pn）,stomatal conductance（Gs）,transpiration rate（Tr）,stomatal limit value（Ls）,and water use efficiency（WUE）of S.divaricata leaves significantly increase,all reaching their peak under Na HCO₃:Na₂CO₃=1:0,10 g/kg treatment;The maximum photochemical efficiency（Fv/Fm）,actual light energy conversion efficiency（Y（II））,electron transfer rate （ETR）,and photochemical quenching coefficient（q P）all significantly decreased,while the non photochemical quenching coefficient（NPQ）significantly increased,indicating that under different alkaline salt treatments,S.divaricata loses excessive light energy through fluorescence and heat dissipation to protect normal plant growth.5.The effect of different alkaline salts on the absorption and transportation of inorganic ions in S.divaricata.Different alkaline salt treatments increased the Na⁺content in the body of S.divaricata,but more Na⁺accumulated in the petioles.The maximum tolerance of Na⁺in S.divaricata petioles was 42 mg/g;Different alkaline salt treatments reduced K⁺/Na⁺and Ca²⁺/Na⁺values in S.divaricata,but TS_K,Na,TS_Ca,Na increased significantly,indicating that S.divaricata had strong selectivity for transporting K⁺and Ca²⁺from roots to leaves,while weak selectivity for transporting Na⁺,so as to maintain high K⁺/Na⁺values in histiocyte to ensure normal physiological metabolism.6.Comprehensive evaluation of different alkaline salts on S.divaricata.Based on the results of principal component analysis and membership function analysis,it was found that growth indicators,antioxidant enzyme activity,TP,MDA,hesperidol glycoside,5-O-methylvisaminide,chlorophyll fluorescence parameters,TS_K,Na,and TS_Ca,Na are sensitive to alkaline salt treatment and can be used in practice to monitor and evaluate the salt tolerance of S.divaricata.S.divaricata can grow well when the alkaline salt content is below 10 g/kg,with Na₂CO₃ content not exceeding 0.5 g/L.