Abstract

The efficiency of oxygenic photosynthesis is critically dependent on the tight regulation of electron transport, a process largely governed by the pH gradient across the thylakoid membrane. This proton-motive force, generated by light-driven electron flow, controls key regulatory mechanisms such as the activity of the ATP synthase and the induction of non-photochemical quenching (NPQ). This study presents an **in silico** model designed to optimize oxygenic photosynthesis by precisely analyzing the **pH-regulation of electron transport** in chloroplasts. The model integrates the kinetics of proton translocation, buffering capacities of the thylakoid lumen, and the pH-sensitivity of the cytochrome $b_6f$ complex and Photosystem II. Our simulations reveal that the optimal photosynthetic efficiency is achieved within a narrow range of lumenal pH, where the balance between ATP production and photoprotection is maximized. Specifically, the model identifies a critical feedback loop where minor fluctuations in lumenal pH lead to significant, non-linear changes in electron transport rate, suggesting a highly sensitive regulatory mechanism. These findings provide a quantitative framework for understanding the dynamic control of photosynthesis and offer theoretical targets for genetic engineering aimed at enhancing crop yield and photosynthetic performance.