Mechanistic Modeling Reveals Adaptive Photosynthetic Strategies of <em>Eichhornia crassipes</em>: Implications for Aquatic Plant Physiology and Invasion Dynamics

The invasive aquatic macrophyte Eichhornia crassipes (water hyacinth) exhibits exceptional adaptability across a wide range of light environments, yet the mechanistic basis of its photosynthetic plasticity under both high and low light stress remains poorly resolved. This study integrates chlorophyll fluorescence and gas exchange analyses to evaluate three photosynthetic models—rectangular hyperbola (RH), non-rectangular hyperbola (NRH), and the Ye mechanistic model—in capturing light-response dynamics in E. crassipes. The Ye model provided superior accuracy (R2 &gt; 0.996) in simulating net photosynthetic rate (Pn) and electron transport rate (J), outperforming empirical models that overestimated Pnmax by 36–46% and Jmax by 1.5–24.7% and failed to predict saturation light intensity. Mechanistic analysis revealed that E. crassipes maintains high photosynthetic efficiency in low light (LUEmax = 0.030 mol mol−1 at 200 µmol photons m−2 s−1) and robust photoprotection under strong light (NPQmax = 1.375, PSII efficiency decline), supported by a large photosynthetic pigment pool (9.46 × 1016 molecules m−2) and high eigen-absorption cross-section (1.91 × 10−21 m2). Distinct thresholds for carboxylation efficiency (CEmax = 0.085 mol m−2 s−1) and water-use efficiency (WUEi-max = 45.91 μmol mol−1 and WUEinst = 1.96 μmol mmol−1) highlighted its flexible energy management strategies. These results establish the Ye model as a reliable tool for characterizing aquatic photosynthesis and reveal how E. crassipes balances light harvesting and dissipation to thrive in fluctuating environments. Insights gained have implications for both understanding invasiveness and managing eutrophic aquatic systems.