Abstract: Aims In order to explore the effect of root-derived volatile compounds from Chinese fir (Cunninghamia lanceolata) on the growth of neighboring plants under low phosphorus stress, a controlled indoor pot experiment was conducted. Methods One-year-old seedlings of the same clonal line of Chinese fir were selected as the study subjects. The experiment was designed with two phosphorus supply treatments: a sufficient phosphorus supply treatment (1.0 mmol/L KH2PO4) and a no phosphorus supply treatment (0 mmol/L KH2PO4). n-Decane, as an exogenous volatile organic compound, was applied to each pot at a concentration of 0.3 mL to simulate the release of volatile organic compounds from the roots of Chinese fir. The selection of n-decane was based on its significant expression under phosphorus-deficient conditions, as observed in previous studies. This allowed the assessment of the impact of root-exuded volatile organic compounds on various growth-related parameters of neighboring plants, including root morphology, physiological traits, and molecular-level changes. In particular, the root morphological and physiological parameters included root length, surface area, specific root length, specific surface area, as well as phosphorus content and phosphorus use efficiency Important findings Compared to the sufficient phosphorus supply treatment, the addition of n-decane under no phosphorus supply treatment significantly affected the root morphological growth of Chinese fir seedlings. In particular, root length was decreased by 37.4%, dry mass was reduced by 29.3%, and specific surface area was increased by 54.1%. Proteomic analysis of the roots revealed that under phosphorus deficiency, the addition of n-decane increased the expression of glycine synthase (Glutamate-glyoxylate aminotransferase) by 1.3-fold, while the expression of glycine dehydrogenase (Threonine aldolase) decreased significantly by 33.3%, leading to a accumulation of glycine. Glycine played a crucial role in the adjustment of root morphology. Regarding phosphorus utilization, compared to the adequate phosphorus treatment, n-decane addition under phosphorus-deficient conditions resulted in a significant decrease in root phosphorus content by 15.1%, but an increase in root phosphorus use efficiency by 19.0%. In conclusion, the addition of n-decane not only significantly enhances the phosphorus use efficiency in Chinese fir roots but also influences the regulation of root morphology by modulating glycine levels. This dual effect contributes to improving the adaptability of Chinese fir seedlings to phosphorus deficiency stress, potentially through mechanisms that optimize both phosphorus acquisition and root growth under phosphorus-deficient conditions. The results of this study offer new insights into the potential allelopathic mechanisms mediated by volatile organic compounds and their broader implications for forest management and plant community dynamics.

Key words: phosphorus utilization strategies, low phosphorus stress, root volatile organic compounds, n-decane, Cunninghamia lanceolata