Cadmium ion (Cd²⁺) stress is a major abiotic stressor affecting plant photosynthesis. However, the impact of sustained high-concentration Cd stress on the photosynthetic electron transport chain of aquatic plants is currently unclear. Here, prompt fluorescence (PF), delayed fluorescence (DF), and P700 signals were simultaneously measured to investigate the effect of Cd stress on photosynthesis in water dropwort [Oenanthe javanica (Blume) DC.]. We aimed to elucidate how Cd stress continuously affects the electron transport chain in this species. The PF analysis showed that with prolonged Cd stress, the F_J, F_I and F_P steadily decreased, accompanied by a positive shift in the K-band and L-band. Moreover, JIP-test parameters, including TR_O/ABS, ABS/CS_O, TR_O/CS_O and PI_ABS, were significantly reduced. The P700 signals showed that exposure to Cd stress hindered both the fast decrease and slow increase phases of the MR transient, ultimately resulting in a gradual reduction in both V_PSI and V_PSII−PSI. The DF analysis showed a gradual decrease in the I₁ and I₂ values as the duration of stress from Cd increased. The above results suggested that Cd stress affected the photosynthetic electron transport in water dropwort by influencing the amount of active PSII and PSI, primarily affecting PSII RCs in the early to mid-stages and PSI reductive activity in the later stage.

Climate change poses a threat to both the natural habitat and the sustainable production of Euryale ferox, a valuable aquatic crop. To address this issue, our study employed an optimized Maximum Entropy (MaxEnt) model to project the climatic suitability of E. ferox distribution in China for the 2030-2070 s under four climate scenarios. Utilizing 130 occurrence records of E. ferox and 20 ecological factors, we identified four primary factors influencing the distribution of E. ferox. The optimal conditions for E. ferox include elevations below 184.8 m, the temperature of the warmest season exceeds 25.7°C, the precipitation of the wettest month ranging between 167 and 718 mm, and precipitation over 9.5 mm in the driest month. The accuracy of the MaxEnt model predictions was comprehensively evaluated by the area under the ROC curve (AUC = 0.942) and the true skill statistic (TSS = 0.783), indicating its effectiveness in forecasting suitable environments. We also found that the current areas of highly and moderately suitable habitats are 0.909 × 10⁵ km² and 3.324 × 10⁵ km², respectively. Compared to the current scenario, future projections indicate a significant increase in suitable areas. Furthermore, except for SSP245, the distribution centroid is projected to move southwestward then northward under other climate scenarios. These findings suggest that climate change may broadly benefit the expansion of E. ferox, offering critical insights for the formulation of regional conservation and cultivation strategies.