The relationship of leaf photosynthetic traits - V sub(cmax) and J sub(max) - to leaf nitrogen, leaf phosphorus, and specific leaf area: a meta-analysis and modeling study

Great uncertainty exists in the global exchange of carbon between the atmosphere and the terrestrial biosphere. An important source of this uncertainty lies in the dependency of photosynthesis on the maximum rate of carboxylation (V sub(cmax)) and the maximum rate of electron transport (J sub(max)). Understanding and making accurate prediction of C fluxes thus requires accurate characterization of these rates and their relationship with plant nutrient status over large geographic scales. Plant nutrient status is indicated by the traits: leaf nitrogen (N), leaf phosphorus (P), and specific leaf area (SLA). Correlations between V sub(cmax) and J sub(max) and leaf nitrogen (N) are typically derived from local to global scales, while correlations with leaf phosphorus (P) and specific leaf area (SLA) have typically been derived at a local scale. Thus, there is no global-scale relationship between V sub(cmax) and J sub(max) and P or SLA limiting the ability of global-scale carbon flux models do not account for P or SLA. We gathered published data from 24 studies to reveal global relationships of V sub(cmax) and J sub(max) with leaf N, P, and SLA. V sub(cmax) was strongly related to leaf N, and increasing leaf P substantially increased the sensitivity of V sub(cmax) to leaf N. J sub(max) was strongly related to V sub(cmax), and neither leaf N, P, or SLA had a substantial impact on the relationship. Although more data are needed to expand the applicability of the relationship, we show leaf P is a globally important determinant of photosynthetic rates. In a model of photosynthesis, we showed that at high leaf N (3 gm super(-2)), increasing leaf P from 0.05 to 0.22 gm super(-2) nearly doubled assimilation rates. Finally, we show that plants may employ a conservative strategy of J sub(max) to V sub(cmax) coordination that restricts photoinhibition when carboxylation is limiting at the expense of maximizing photosynthetic rates when light is limiting. Great uncertainty exists in the global exchange of carbon between the atmosphere and the terrestrial biosphere. To reduce this uncertainty we analysed data collected in the literature from across the globe on the maximum rate of carboxylation (V sub(cmax)) and the maximum rate of electron transport (J sub(max)) in relation to plant nutrient status indicated by the traits: leaf nitrogen (N), leaf phosphorus (P), and specific leaf area (SLA). V sub(cmax) was strongly related to leaf N and increasing leaf P substantially in