Growth adaptation of Nitraria sibirica in drought: Hormone-mediated flavonoid accumulation, altered metabolic pathways, and decreased network complexity

Abstract

Drought is a severe abiotic stress condition that impedes plant growth and development. During adaptation to drought conditions, plants release numerous small-molecule compounds that enhance their adaptive capacity. Nitraria sibirica Pall. is an ecologically valuable plant; however, its metabolic adaptation mechanisms in different soil–water habitats have not been clearly reported. In this study, high-performance liquid chromatography (HPLC) and non-targeted metabolomic techniques were combined to investigate the growth adaptation mechanisms of N. sibirica in different soil environments. The results showed that the response of N. sibirica leaves to drought mainly manifested as a significant increase in abscisic acid (ABA) levels and a significant decrease in gibberellin (GA) levels (except during flowering). Drought led to the production of more metabolites during the growth and development of N. sibirica but reduced the complexity of the metabolite network. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed significant differences in the growth adaptation pathways of metabolites between the two habitats. In riparian habitats (RH), the phenylpropane biosynthesis pathway was significantly upregulated, while the synthesis of cutin, suberin, wax, α-linolenic acid metabolism, and linoleic acid metabolism was significantly downregulated. However, the tryptophan metabolism pathway was consistently downregulated in desert habitats (DH), with flavonoid and flavonol biosynthesis pathways playing important roles in drought resistance. The random forest model showed that the soil environment explained 3.21–94.34 % of the metabolite variation. Furthermore, structural equation modeling demonstrated that soil water had an indirect and positive effect on flavonoid metabolites by regulating ABA. This study revealed the adaptive mechanisms of hormones and metabolites in N. sibirica under drought conditions. It identified certain hormones that could potentially be harnessed for the development of plant additives, providing potential opportunities for exploring new stress adaptation strategies and developing new plant drought resistance products.