Relationship Between Leaf Maximum Carboxylation Rate and Chlorophyll Content Preserved Across 13 Species

Abstract The leaf maximum carboxylation rate ( V cmax ) is a crucial parameter in determining the photosynthetic capacity of plants. Providing accurate estimates of leaf V cmax , that cover large geographic areas and incorporate plant seasonality is central to correctly predicting carbon fluxes within the terrestrial global carbon cycle. Chlorophyll, as the main photon‐harvesting molecule in leaves, is closely linked to plant photosynthesis. However, how the nature of the relationship between the leaf maximum carboxylation rate (scaled to 25°C; V cmax,25 ) 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 V cmax,25 and leaf chlorophyll content across different plant types and verify it using field experiments. Measurements of leaf chlorophyll content (Chl) and CO 2 response curves were made on 283 crop, shrub, tree, and vegetable leaves, across 13 species, in China and southern Ontario, Canada. A strong relationship was found between the leaf V cmax,25 and chlorophyll content across different plant types ( R 2 = 0.65, p < 0.001). Cross‐validation showed that the model performs well, producing an RMSE value of 15.4 μmol m −2 s −1 . The results confirm that leaf chlorophyll content can be a reliable proxy for estimating V cmax,25 , opening the door to accurate, spatially continuous estimates of V cmax,25 at the global scale.