Phosphorus relieves aluminum toxicity in oil tea seedlings by regulating the metabolic profiling in the roots

Oil tea (Camellia oleifera Abel.) is an important edible oil tree mainly grown in acidic soils, whose growth and yield can be severely limited due to soil aluminum (Al) toxicity and phosphorus (P) deficiency. In this study, we investigated the physiological and metabolic responses of oil tea to Al and P treatment for an 8-week duration. Al reduced root length, root volume, and plant biomass, while P addition alleviated the effects of Al toxicity. P addition increased P content and reduced Al accumulation in roots. The profiles of 58 metabolites were significantly changed in roots of oil tea seedlings. Al toxicity increased various amino acids, but decreased many kinds of organic acids and carbohydrates. Interestingly, P addition reduced the amino acids accumulation which were induced by Al toxicity, while only a few organic acids changed under P supply. Most carbohydrates, including sucrose and glucose, significantly increased with P addition under Al toxicity. Results indicated that Al toxicity increased the accumulation of amino acids and reduced the accumulation of organic acids and carbohydrates, while the addition of P promoted root growth by alleviating the inhibition of protein synthesis and increasing carbohydrates content. However, P addition did not increase the organic acids content in roots.