Elevated CO₂ promotes the acquisition of phosphorus in crop species differing in physiological phosphorus-acquiring mechanisms

Background and aims: Crop species differ in phosphorus (P) acquisition in P-limiting environments. However, it is not fully understood how elevated atmospheric CO2 concentrations affects these P acquisition mechanisms and the plant's ability to acquire P from soil. This study aimed to investigate the effect of elevated CO2 on P acquisition in crop species with contrasting P acquisition mechanisms. Methods: White lupin, faba bean, canola and near-isogenic wheat lines with and without citrate efflux were grown for 70 days in a P-deficient Chromosol soil under ambient (400 ppm) and elevated (800 ppm) CO2. Plant P uptake and P transformation in the rhizosphere were determined. Results: Elevated CO2 promoted total P uptake in white lupin and canola by 84% and 48%, respectively, and decreased the P uptake in the non-citrate-exuding wheat (by 24%) but not the exuding wheat. In white lupin, elevated CO2 enhanced phosphatase activity and depletion of organic P in the rhizosphere. Elevated CO2 increased P uptake by increasing root length which allowed canola to exploit a greater volume of soil for P. In the rhizosphere of faba bean, NaOH-extractable inorganic P was greater under elevated CO2. Conclusion: Crops which rely on organic acid exudation and phosphatases appear to be better adapted to acquiring P under elevated CO2.