Differential effects of exogenous VOCs on the growth and stress responses of Cunninghamia lanceolata seedlings under low phosphorus

This study investigates how exogenous volatile organic compounds (VOCs) influence the root responses of Cunninghamia lanceolata under nutrient limitations. Specifically, we assessed the differential effects of syringic acid and 1-butene on root morphology, phosphorus acquisition, and stress resilience. Clonal Chinese fir seedlings were utilized to test the effects of treatment with these two exogenous VOCs under both phosphorus supply (1.0 mM KH₂PO₄) and no phosphorus supply (0 mM KH₂PO₄) treatments in a controlled pot experiment. Compared to syringic acid, 1-butene significantly enhanced root morphological traits, including root length, specific surface area, and root volume. These morphological changes enhanced the root's ability to acquire phosphorus. Moreover, the addition of 1-butene increased the underground phosphorus use efficiency (PUE) by 25.6% compared to the addition of syringic acid. Furthermore, the addition of 1-butene stimulated higher activity of antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD). Proteomic analysis revealed that 1-butene induced significant changes in root protein expression, particularly in proteins associated with stress responses, phenylpropanoid biosynthesis, and phosphate transport. Compared to syringic acid, 1-butene promoted the differential expression of phosphate transporter proteins, indicating its beneficial effects on the root systems of Chinese firs under low-phosphorus stress. These findings underscore the potential of 1-butene in promoting root efficiency and phosphorus acquisition in forest species, providing insights for enhancing plant adaptation to nutrient limitations.