The researchers studied the chlorophyll and photosynthetic fluorescence of dominant submerged plants in Nanjishan Wetland of Poyang Lake in winter. They found that Hydrilla verticillata and Vallisneria natans were the main species, with H. verticillata having higher chlorophyll content and stronger photosynthesis than V. natans. H. verticillata also had a significant light-harvesting capacity. The photosynthetic efficiency of both plants was lower than optimal, suggesting they may be under external stress that could harm their ability to photosynthesize.