Objective   Studying the response of growth and metabolic characteristics of Artemisia scoparia to precipitation changes can provide reference for vegetation restoration and reconstruction in desert steppe.

  Method  Test method of precipitation control was adopted and the growth characteristics of A. scoparia under the condition of precipitation change (30% water increase treatments, IT; check treatments, CK; 30% water decrease treatments, DT) were continuously observed from 2017 to 2020, and its metabolites were determined to explore the response mechanism of growth response and metabolic adaptation of A. scoparia to precipitation change.

  Result  The results showed that precipitation changes had little effect on the growth characteristics of A. scoparia in the year with more precipitation (2018), while the aboveground biomass, density, plant height and crown width of A. scoparia had significant response to precipitation changes in the dry year (2020). Seven hundreds and seventy two metabolites were detected in the stem and leaf mixture of A. scoparia, including flavonoids, phenolic acids, lipids, etc. The 43 metabolites with significant differences among different precipitation treatments were mainly flavonoids, phenolic acids, organic acids, lipids, amino acids and their derivatives. There were 52 individual differential metabolites in the increased and decreased water treatment, and the differential metabolites were mainly up-regulated, which accounted for 76.07% of differential metabolites, while there were only 2 common differential metabolites in common among the three treatments. The results indicated that the precipitation change in desert steppe was an important factor affecting the growth and metabolism characteristics of A. scoparia. In metabolic pathway, precipitation changes mainly affected anthocyanin biosynthesis, arginine biosynthesis and starch and sucrose metabolism in stem and leaf mixture of A. scoparia.

  Conclusion  A. scoparia in desert steppe adapted to the change of precipitation by enhancing the phenotypic plasticity of aboveground biomass, density, plant height and crown width. The phenotypic plasticity variation in dry years of precipitation was more obvious than that in wet years. Precipitation can significantly change the metabolites of stem and leaf of A. scoparia, which may be the expression of physiological plasticity of A. scoparia under drought environment. Although the KEGG metabolic pathway of A. scoparia under different precipitation treatments was found, the specific regulation mechanism of the differential pathway needs to be further explored.