Study on Purification Effect of Paspalum distichum L. on Swine Wastewater Uptake and Translocation of Heavy Metals in Dominant Plants of Soil Seed Banks INTRODUCED TO A LEAD / ZINC MINE TAILINGS POND Facultative Apospory in Tetraploid Paspalum distichum L. Effects of submergence on the antioxidative enzymes and carbohydrate contents of Paspalum distichum Effect of Long-time and Deep Submergence on Recovery Growth and Photosynthesis of Three Grass Species in Three Gorges Reservoir Area Permeability and Supplement Structures of Stems of Paspalum distichum