Metabolomic profiling reveals root exudation pattern as regulated by phosphorus and light in contrasting rice cultivars

Phosphorus (P) fixation in soils constrains its bioavailability, driving the evolution of adaptive strategies in plants, such as root morphology plasticity and exudation. This study systematically compared changes in root exudation pattern in a low-P-tolerant rice cultivar “Dalixiang” and a P-susceptible cultivar “Meixiangzhan” under different light intensities and P supplies. The results showed that, (1) Under P deficiency, Dalixiang exhibited a significantly increased root-to-shoot ratio, whereas Meixiangzhan showed a weaker ability to cope with P deficiency and low light. (2) Light intensity exerts a quantitatively greater influence on root exudation profiles than P supply, as evidenced by both the number of differential metabolites (301 vs. 185) and the magnitude of fold changes in key compounds. (3) The tolerant cultivar exhibited greater metabolic flexibility, releasing a broader spectrum of exudates across environments. Key pathways, including amino acid metabolism, were reconfigured by both stimuli. (4) Several previously unreported metabolites co-regulated by light intensity and P availability demonstrated their functional relevance. Notably, α-methylene-γ-butyrolactone significantly promoted root and shoot growth under P deficiency, while citraconic acid and xanthoxic acid enhanced P uptake. Our findings establish that light and P status dictates root physiological and metabolic traits, ultimately modulating rhizosphere P mobilization. This work provides a mechanistic framework for improving P-use efficiency in crops by leveraging the interplay between light management and root-mediated processes. Light overrides P availability in reshaping root exudation patterns in rice. A P-tolerant cultivar exhibits greater metabolic flexibility, and several key exudates enhance plant growth under P deficiency.