The invasive aquatic macrophyte Pontederia 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 integrated 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 P. crassipes. The Ye model provided superior accuracy (R² > 0.996) in simulating the net photosynthetic rate (P_n) and electron transport rate (J), outperforming empirical models that overestimated P_nmax by 36–46% and J_max by 1.5–24.7% and failed to predict saturation light intensity. Mechanistic analysis revealed that P. crassipes maintains high photosynthetic efficiency in low light (LUE_max = 0.030 mol mol⁻¹ at 200 µmol photons m⁻² s⁻¹) and robust photoprotection under strong light (NPQ_max = 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). Unlike terrestrial plants, its floating leaves experience enhanced irradiance due to water-surface reflection and are decoupled from water limitation via submerged root uptake, enabling flexible stomatal and energy regulation. Distinct thresholds for carboxylation efficiency (CE_max = 0.085 mol m⁻² s⁻¹) and water-use efficiency (WUE_i-max = 45.91 μmol mol⁻¹ and WUE_inst = 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 P. crassipes balances light harvesting and dissipation to thrive in fluctuating environments. These resulting insights have implications for both understanding invasiveness and managing eutrophic aquatic systems.

Understanding how environmental factors regulate photosynthetic energy partitioning is crucial for enhancing crop resilience in future climates. This study investigated the light-response dynamics of sweet sorghum (Sorghum bicolor L. Moench) leaves under combinations of CO₂ concentrations (250, 410, and 550 μmol mol⁻¹) and temperatures (30 °C and 35 °C), using integrated chlorophyll fluorescence measurements and mechanistic photosynthesis modeling. Our results revealed that elevating CO₂ from 250 to 550 μmol mol⁻¹ significantly increased the maximum electron transport rate (J_max) by up to 57%, and enhanced the effective light absorption cross-section (σ′_ik) by 64% under high light and elevated temperature (35 °C), indicating improved photochemical efficiency and light-harvesting capability. Concurrently, these adjustments reduced PSII down-regulation. Increased temperature stimulated thermal dissipation, reflected in a rise in non-photochemical quenching (NPQ) by 0.13–0.26 units, accompanied by a reduction in the number of excited-state pigment molecules (N_k) by 20–33%. The strongly coordinated responses between quantum yield (Φ_PSII) and σ′_ik highlight a dynamic balance among photochemistry, heat dissipation, and fluorescence. These findings elucidate the synergistic photoprotective and energy-partitioning strategies that sweet sorghum employs under combined CO₂ enrichment and heat stress, providing mechanistic insights for optimizing photosynthetic performance in C₄ crops in a changing climate.

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 > 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.