| Glycyrrhiza uralensis Fisch.is an important Chinese herbal medicine in China and is used in a large amount in the market.However,the poor quality of cultivated licorice has not been replaced by wild licorice due to the increasing scarcity of wild resources so far.Therefore,improving the quality of artificial cultivation of licorice has become an urgent problem to be solved.The previous research of the research group showed that the accumulation of active ingredients of cultivated licorice is closely related to the respiratory metabolism and nitrogen metabolism of the root system,and gamma-aminobutyric acid is closely related to the respiratory metabolism and the accumulation of active ingredients in the root system.At the same time,exogenous ammonium nitrogen,glutamate and gamma-aminobutyric acid can promote the respiratory metabolism of licorice roots.Therefore,we used the licorice seedlings of the year as experimental materials to explore the dynamic changes of respiratory metabolism and nitrogen metabolism in the licorice roots with plant growth and development.And using gray correlation analysis to explore correlation between five active ingredients and gammaaminobutyric acid metabolism related to respiratory metabolism and nitrogen metabolism.In addition,a 15N microtracing test was set up to study the accumulation and distribution of exogenous ammonium nitrogen in the licorice plants.At the same time,the hydroponic licorice seedlings were used as experimental materials to study the mechanism of nitrogen metabolism and respiratory metabolism of the root system.The results of the experiment can lay a theoretical foundation for the study of the regulation mechanism of active ingredients accumulation of cultivated licorice,and it is of great significance to improve the quality of artificially cultivated licorice.The main findings are as follows:1、The respiratory metabolism and nitrogen metabolism of licorice roots has obvious dynamic changes with plant growth and development.The respiratory substrate(soluble sugar)of licorice root showed a "decrease-elevation-decrease" trend with August being its rapid accumulation period.In the respiratory metabolism of licorice roots,TCA cycle mainly synthesized oxaloacetate and malic acid,and it was a period of strong metabolism from July to August.The metabolism of oxaloacetate and citric acid was the most prosperous in the TCA cycle.The total organic acids,oxaloacetate,succinate acid and alpha-ketoglutarat in the TCA cycle in the respiratory metabolism of licorice root showed a "decrease-increase-increase" trend,and the total organic acids and oxaloacetate rapidly accumulated from late July to early August,while succinic acid and α-ketoglutarate rapidly accumulated from early August to early September.The total free amino acids in the nitrogen metabolism of licorice showed a gradually increasing trend with plant growth and development.And the nitrogen metabolism process of the roots was mainly synthetic asparagine after August,and its trend was consistent with total free amino acids,while y-aminobutyric acid,aspartic acid,and glutamine showed "increasingdecreasing-increasing" trends.2、The five active ingredients of licorice have obvious dynamic changes with plant growth and development.The trend of glycyrrhizic acid was increasing with time,while the changes of liquiritin and liquiritigenin were alternated with time.The content of isoliquiritin showed a trend of "decrease-increase-decrease"with time.The trend of isoliquiritigenin was a "singlepeak" curve with time.The period from late July to early August was the period of rapid accumulation of glycyrrhizic acid,liquiritin and isoliquiritin.However,August was the period of rapid accumulation of liquiritigenin and isoliquiritigenin.3、The correlations between the five active ingredients of licorice and nitrogen metabolism related to the metabolism of y-aminobutyric acid are different.Glycyrrhizic Acid,liquiritin,liquiritigenin and isoliquiritigenin were more closely related to succinic acid in TCA cycle of respiratory metabolism,while isoliquiritin was more closely related to oxaloacetate.The five active ingredients were more closely to alanine in nitrogen metabolism,Secondly,glycyrrhizic acid was more closely to aspartic acid,Liquiritin and Isoliquiritin were more closely to glutamine,Liquiritigenin and Isoliquiritigenin and were more closely to glutamate.4、Exogenous ammonium nitrogen enters the licorice plant with obvious dynamic changes.Nitrogen accumulation of licorice showed a gradually trend with plant the growth and development.The period from late July to the early August was a period of rapid growth.The absorption capacity of exogenous ammonium nitrogen in different organs of licorice showed that roots and stems had the highest absorption capacity in the middle of July,while leaves had the highest absorption capacity in the late July.The Absorption and utilization of exogenous ammonium nitrogen in different organs of licorice plants were:leaf>stem>root in early growth stage,leaf>root>stem in late growth stage.At the same time,adding appropriate amount of ammonium nitrogen was beneficial to increase the nitrogen fertilizer utilization rate of licorice.5、Exogenous ammonium nitrogen acts on the respiratory metabolism of the roots through the metabolism of gamma-aminobutyric acid.Appropriate amount of ammonium nitrogen can promote the respiration of licorice roots,but the excessive ammonium nitrogen concentration will inhibit root respiration.The introduction of exogenous ammonium into the licorice roots can be converted into gamma-aminobutyric acid through nitrogen metabolism,and can promote the metabolism of root gamma-aminobutyric acid and the synthesis of succinic acid in the TCA cycle of respiratory metabolism.At the same time,the appropriate amount of ammonium nitrogen is favorable for the transformation of exogenous nitrogen into aspartic acid,while a high nitrogen concentration is more conducive to the conversion of exogenous nitrogen to alanine. |
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