The interplay between drought and P scarcity shapes resilience to stress in Quercus spp. by modulating metabolomic profiles

Background and Aims Plant resilience to drought conditions is modulated by physiological and metabolic responses, including the accumulation of antioxidant metabolites. These mechanisms can be in influenced by nutrient availability, especially phosphorus (P). In European mixed forests, native species with high resource demands often compete with more efficient alien species, whose advantages under abiotic stress can enhance their invasiveness. This study investigates how drought and P availability affect the resilience of two Quercus species differing in stress tolerance and resource use efficiency. Methods We conducted a mesocosm experiment in which the native Q. robur (EO) and alien Q. rubra (RO) were grown under well-watered or drought conditions, with or without P supplementation. Leaf gas exchange and stem water potential were measured, leaves and soil were chemically characterized, and metabolite biosynthesis was investigated using an omics approach. Results During drought, the metabolism of P-supplied EO shifted toward the accumulation of phenylpropanoids, flavonoids, saikosaponins, mannitol, and long-chain fatty acids, which are compounds known for their antioxidant, osmoprotectant, and membrane-stabilizing functions. Conversely, RO plants displayed a more conservative metabolic profile, with limited changes in response to P supply. Under P deficiency, RO accumulated secondary metabolites such as phenylpropanoids and alkaloids, highlighting its ability to withstand with combined nutrient and water stress. Conclusions Our results reveal contrasting adaptive strategies: EO is more susceptible to drought stress, but its resilience can be modulated by P availability, whereas RO maintains more stable physiological and metabolic functions, consistent with higher nutrient-use efficiency.