e‐photosynthesis: a comprehensive dynamic mechanistic model of C3 photosynthesis: from light capture to sucrose synthesis

ABSTRACT Photosynthesis is arguably the most researched of all plant processes. A dynamic model of leaf photosynthesis that includes each discrete process from light capture to carbohydrate synthesis, e‐photosynthesis, is described. It was developed by linking and extending our previous models of photosystem II (PSII) energy transfer and photosynthetic C3 carbon metabolism to include electron transfer processes around photosystem I (PSI), ion transfer between the lumen and stroma, ATP synthesis and NADP reduction to provide a complete representation. Different regulatory processes linking the light and dark reactions are also included: Rubisco activation via Rubisco activase, pH and xanthophyll cycle‐dependent non‐photochemical quenching mechanisms, as well as the regulation of enzyme activities via the ferredoxin‐theoredoxin system. Although many further feedback and feedforward controls undoubtedly exist, it is shown that e‐photosynthesis effectively mimics the typical kinetics of leaf CO2 uptake, O2 evolution, chlorophyll fluorescence emission, lumen and stromal pH, and membrane potential following perturbations in light, [CO2] and [O2] observed in intact C3 leaves. The model provides a framework for guiding engineering of improved photosynthetic efficiency, for evaluating multiple non‐invasive measures used in emerging phenomics facilities, and for quantitative assessment of strengths and weaknesses within the understanding of photosynthesis as an integrated process. Although the process of photosynthesis from light capture to carbohydrate synthesis has been largely known for some time, a complete dynamic process model representing each discrete step has been lacking. e‐Photosynthesis described here provides this platform and is shown to reproduce in silico, quantitatively and qualitatively, responses of leaf gas exchange, electron transport, chlorophyll fluorescence and biochemical fluxes observed in vivo. The model provides a design engineering tool for selecting targets in a system of over 100 potential targets and many thousands of permutations.