Integrated modeling and observational analysis of light-saturated electron transport rates in four C₃ species

Currently, there is still a lack of systematic comparison between the light-saturated maximum electron transport rate (J_max) predicted by the Farquhar-von Caemmerer-Berry (FvCB) model and the empirically observed whole-chain electron transport rate (J_f-max) measured directly through experiments, which is essential for validating the reliability and predictive capability of the photosynthesis model. This study presents a comparative evaluation of the FvCB model's ability to estimate the J_max in four C₃ species: Ipomoea batatas, Pachyrhizus erosus, Capsicum annuum, and Abelmoschus esculentus. By integrating gas exchange measurements and chlorophyll fluorescence data, we analyzed A_n-C_i curves under saturating irradiance to derive J_max values using two FvCB sub-models (I and II) and compared these estimates with J_f-max. Results revealed significant discrepancies: Sub-model II consistently overestimated J_max relative to J_f-max in three species (I. batatas, P. erosus, and C. annuum), while Sub-model I showed no statistical deviation. Notably, A. esculentus exhibited anomalous overestimations by both sub-models, with J_max exceeding J_f-max-a contradiction of theoretical stoichiometry. These findings highlight limitations in the universal applicability of FvCB sub-models, particularly regarding assumptions of electron partitioning among assimilatory and non-assimilatory pathways. However, the empirical model developed by Ye et al. could accurately and reliably estimate J_f-max values for all four C₃ species. The study underscores the need for model refinements to better account for species-specific electron transport dynamics and environmental interactions, advancing the accuracy of photosynthetic predictions in ecological and agricultural contexts.