C₃ plants converge on a universal relationship between leaf maximum carboxylation rate and chlorophyll content

The leaf maximum carboxylation rate (Vcmax) is one of the crucial parameters in determining the photosynthetic capacity of plants. Providing accurate estimates of leaf Vcmax25 that cover large geographic areas and that incorporate plant seasonality is central to correctly predicting carbon fluxes within the terrestrial global carbon cycle. Chlorophyll, as the main photon-harvesting component in leaves, is closely linked to photosynthesis. However, how the nature of the relationship between the leaf maximum carboxylation rate scaled to 25 °C (Vcmax25) and leaf chlorophyll content varies according to plant type is uncertain. In this study, we investigate whether a universal and stable relationship exists between leaf Vcmax25 and leaf chlorophyll content across different C3 plant types from a plant physiological perspective and verify it using field experiments. Measurements of leaf chlorophyll content (Chl) and CO2 response curves were made on 283 crop, shrub, tree and vegetable leaves in China and the Borden Forest Research Station in southern Ontario, Canada. A strong relationship was found between the leaf Vcmax25 and chlorophyll content across different C3 plant types (R2 = 0.65, P 25 across different C3 plant types over space and time, opening the door to accurate spatially continuous estimates of Vcmax25 at the global scale.