The construction of the Three Gorges-Gezhouba Dam cascade hydropower station has changed the water level fluctuation pattern of the habitats for remnant rare and endangered Myricaria laxiflora populations downstream of the dam. The present study utilized biochemical markers of photosynthetic physiology to evaluate the spatiotemporal responses of remnant populations to human-regulated water level fluctuations. The results showed that the photosynthetic physiological activities of remnant M. laxiflora populations underwent a period of rapid growth, followed by a gradual decline in the growth recovery phase after flooding. During the entire experimental period, photosynthetic physiological activities of remnant M. laxiflora populations changed with prolongation of emergence time: specifically, net photosynthetic rate and stomatal conductance initially decreased and then subsequently increased, intercellular carbon dioxide concentrations peaked at mid-phase and transpiration rate continuously increased. The maximum net photosynthetic rate, apparent photosynthetic quantum efficiency and dark respiration rate in the light-response curves of the plants continuously increased during growth. The water level gradient also significantly affected the photosynthetic physiological activities in the remnant populations, i.e. the photosynthetic physiological activities of high-altitude plants were significantly higher than the middle- and low-altitude plants. The changes in photosynthetic pigment content of plants in remnant populations during the growth recovery phase and the entire growth period were similar to those occurring in photosynthetic activities in plants. Further, canonical correspondence analysis showed that photosynthetic physiological activities in the plants were significantly correlated with changes in water levels, emergence time, elevation gradient, soil water and soil nitrogen contents. Therefore, the artificial regulation of water level fluctuations by large hydropower stations will inevitably affect the photosynthetic activities and growth of remnant M. laxiflora populations.

中文翻译：

---

剩余的洋紫阳种群对水位波动的时空光合生理响应。

三峡-葛洲坝大坝梯级水电站的建设改变了该坝下游剩余的稀有和濒危的洋紫阳种群的栖息地的水位波动模式。本研究利用光合生理的生化标志物来评估剩余种群对人类调节的水位波动的时空响应。结果表明，剩余的M. laxiflora种群的光合生理活动经历了一个快速的增长期，洪水后其恢复阶段逐渐下降。在整个实验过程中，剩余Laxiflora种群的光合生理活性会随着出现时间的延长而发生变化：具体而言，净光合速率和气孔导度先降低后升高，细胞间二氧化碳浓度在中期达到峰值，蒸腾速率不断提高。在生长过程中，植物的光响应曲线中的最大净光合速率，表观光合量子效率和暗呼吸速率不断增加。水位梯度也显着影响剩余种群的光合生理活性，即高海拔植物的光合生理活性明显高于中低海拔植物。在恢复期和整个生长期中，剩余种群中植物光合色素含量的变化与植物光合作用中发生的变化相似。典范对应分析表明，植物的光合生理活性与水位，出苗时间，海拔梯度，土壤水分和土壤氮含量的变化显着相关。因此，大型水电站对水位波动的人为调节将不可避免地影响剩余的M. laxiflora种群的光合活动和生长。海拔梯度，土壤水分和土壤氮含量。因此，大型水电站对水位波动的人为调节将不可避免地影响剩余的M. laxiflora种群的光合活动和生长。海拔梯度，土壤水分和土壤氮含量。因此，大型水电站对水位波动的人为调节将不可避免地影响剩余的M. laxiflora种群的光合活动和生长。