| Drought stress is one of the important abiotic stresses that restrict plant growth.Drought will change the morphology and physiological state of plants,thereby stimulating plants to produce antioxidant enzymes,complex metabolites to resist drought.Glycyrrhiza uralensis Fisch.is widely distributed in China,Iran and other countries.It is mainly distributed in Inner Mongolia,Xinjiang and other regions in my country.The effect of water on its growth and quality is very important.However,there are few studies on the metabolic mechanism of licorice under drought conditions.Therefore,in this experiment,two genotypes of licorice were used as the experimental materials(the root surface is reddish brown and brownish yellow,called G1 and G2).This study is the first to use non-targeted metabonomics technology to determine the metabolites in the roots of two genotypes of licorice under different drought conditions.The purpose is to clarify the complex metabolic regulation mechanism of licorice under drought conditions,and to compare the drought resistance of the two genotypes of licorice.It lays a theoretical foundation for studying the molecular response mechanism of licorice,an important medicinal plant or other legumes,in response to drought stress.It is of great significance for improving water use efficiency and screening drought-resistant varieties of licorice.A two-year field experiment was conducted in Qigetai village,Hohhot city,Inner Mongolia Autonomous Region,to explore the accumulation of active ingredients in different growth periods of licorice and its correlation with climate factors,and provide theoretical support for determining the optimal harvest period of licorice.The main research results are as follows:1.When the relative water content of soil was 34%～41%,it was beneficial to increase the root length and root dry weight of licorice,but severe drought reduced its root dry weight.Different moisture gradient treatment increased the antioxidant enzyme activity,MDA and superoxide anion content in the roots and leaves of the two genotypes of licorice,but excessive drought reduced the enzyme activity.Under the same conditions,G1 ensured that it sufferd less oxidative damage by increasing the activity of antioxidant enzymes and less accumulation of MDA.2.When the relative water content of soil was 34%～41%,it was beneficial to increase the content of Liquiritin and Glycyrrhizic acid,and the content of Liquiritin and Glycyrrhizic acid in root of G1 was greater than that of G2 under the same conditions.After 60 d and 90 d of drought,the content of Glycyrrhizic acid in stems and leaves continued to decrease.Under the same conditions,the content of Liquiritigenin and Isoliquiritigenin in stems of G2 was greater than that of G1.3.A total of 2701 metabolites were detected by LC-MS,which were mainly involved in flavonoid biosynthesis,isoflavone biosynthesis,phenylpropane biosynthesis and other pathways.The difference metabolites screened by VIP value were mostly lipids.The effects of drought on amino acids,flavonoids,organic acids and other substances had genotypic differences.As the degree of drought deepens,tryptophan and tyrosine continued to accumulate,increase lipid accumulation,induce the metabolism of flavonoids in licorice.4.The two-year field experiment showed that the content of active ingredients in licorice root was highest in September and October,and the content in stems and leaves accumulated with the growth period.Therefore,in order to obtain better medicinal quality,the best harvest period of licorice is in September and October. |
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