关键词: 隔离降水, 根系分泌物, LC-MS, 糖类, 化学组成, 杉木人工林

Abstract: We simulated drought through 50% isolated rainfall exclusion and collected fine root exudates of Cunninghamia lanceolata during dry and wet seasons. Combined with total organic carbon (TOC) measurements and untargeted metabolomics (LC-MS) analysis, we investigated the seasonal responses of exudation rate and chemical composition of fine root exudates to drought stress. The results showed that there were significant seasonal variations in drought effects on root exudates. During dry season, the unit root length exudation rate and TOC concentration of root exudates decreased by 72.7% and 74.6%. In wet season, they increased by 58.0% and 35.4%, respectively. Organic acids, phenols, and amino acids were the dominant types in the root exudates under drought conditions. In dry season, defensive secondary metabolites such as phenols (e.g., phloroglucinol), flavonoids (e.g., catechin), and phenolic compounds (e.g., methyl mandelate) significantly increased, contributing to enhanced antioxidant capacity and regulation of rhizosphere microbial communities. In contrast, primary metabolites like sugars (e.g., glucose, deoxyribose) and organic acids (e.g., palmitic acid, 2-methylglutaric acid) significantly increased in wet season, promoting osmotic regulation and soil nutrient activation in C. lanceolata. Our results suggest that C. lanceolata adopts a “dry season defense, wet season attack” carbon allocation strategy to cope with drought stress, employing “conservative defense” through defensive secondary metabolites in dry season and “active adaptation” via resource-acquisitive primary metabolites in wet season.

Key words: throughfall exclusion, root exudate, LC-MS, sugar, chemical composition, Cunninghamia lanceolata plantation