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<bold>SUMMARY</bold> While the adverse effects of elevated salinity levels on leaf gas exchange in many crops are not in dispute, representing such effects on leaf photosynthetic rates (A) continues to draw research attention. Here, an optimization model for stomatal conductance (g_c) that maximizesAwhile accounting for mesophyll conductance (g_m) was used to interpret new leaf gas exchange measurements collected for five irrigation water salinity levels. A function between chloroplastic CO₂concentration (c_c) and intercellular CO₂concentration (c_i) modified by salinity stress to estimateg_mwas proposed. Results showed that with increased salinity, the estimatedg_mand maximum photosynthetic capacity were both reduced, whereas the marginal water use efficiencyλincreased linearly. Adjustments ofg_m,λand photosynthetic capacity were shown to be consistent with a large corpus of drought‐stress experiments. The inferred model parameters were then used to evaluate the combined effects of elevated salinity and atmospheric CO₂concentration (c_a) on leaf gas exchange. For a given salinity level, increasingc_aincreasedAlinearly, but these increases were accompanied by mild reductions ing_cand transpiration. Thec_alevel needed to ameliorateAreductions due to increased salinity is also discussed using the aforementioned model calculations.