Leaf phosphorus allocation patterns and photosynthetic phosphorus-use-efficiency in phosphorus-limited conditions

The roles of leaf phosphorus (P) fractions in leaf photosynthetic P-use-efficiency (PPUE) under low soil P, and differences, if any, between legume and non-legume species are largely unknown. We investigated 24 crop species, 13 legumes and 11 non-legumes, for leaf PPUE and P acquisition strategies under low plant-available soil P. Legume species had a lower PPUE (38%), photosynthetic rate per area (A_area; 38%) and per mass (A_mass; 32%), but higher leaf P concentration (19%) than non-legume species. Legume species had a significantly higher nucleic acid P concentration, while percentage of nucleic acid P was higher, but percentage of inorganic P and metabolite P were lower in legumes than in non-legumes. Legume species had significantly greater total root length and carboxylate release than non-legume species. PPUE showed a positive correlation with A_area, A_mass, percentage of lipid P and metabolite P, but a negative correlation with concentrations of inorganic P, nucleic acid P, and leaf P. There was contrasting P-use-efficiency and P acquisition capacities between legume and non-legume species; high photosynthesis rate was associated with a high metabolite P concentration, but low nucleic acid P concentrations were related to a high PPUE. A P mining strategy was associated with a high leaf P concentration and low PPUE. This study provides insight into P use and P acquisition strategies and their correlations among 24 crop species grown under low plant-available soil P conditions.