| To grasp the mechanism of Submerged Macrophytes recession in the large shallow eutrophic lake like Taihu, This paper studied the changes of the Vallisneria natans (Lour.) and Myriophyllum spicatum L. with the nutrients and light intensity and epiphyte based on simulation experiment by analyzing the changes of chlorophyll-a(chl.a) content, Malondialdehyde (MDA) content, antioxidant enzymes activities such as ascorbate peroxidase (APX), superoxide dismutase(SOD),peroxidase(POD) and catalase(CAT). The main results were as follows:(1) In all treatment groups without adding epiphytes, chlorophyll content and the antioxidant enzymes activities of macrophytes were higher in the treatment T2or T3than that in others. It showed that stress resistance of submerged macrophytes would enhanced under suitable levels of nutrients in eutrophic waterbodies, but excessive nitrogen and phosphorus(T4) could inhibit submerged macrophyte resistance.(2) In all treatment groups with adding epiphytes, effect of50%light intensity (58001x-78001x) and the treatment of T2(TN=2.5mg/L,TP=0.25mg/L) on chlorophyll content of Vallisneria natans (Lour.) was the hightest and epiphyte-Vallisneria natans (Lour.) grew well. The results show that on the conditions of light intensity10%and TN2.5mg/L,TP0.25mg/L and treatment group without adding epiphytes, Myriophyllum spicatum L. was more suitable for growing well. The treatment groups100%light intensity with adding epiphytes had suffer from great stress.(3) The unconditional mechanism never exists between epiphyte and submerged macrophyte. The biomass of epiphyte could be controlled when the condition of water was suitable for the submerged plants and for unsuitable conditions senility of leaf had been accelerated when the submerged plants could suffer from oxygen stress.(4) There was a relatively strong correlation between Light intensity and submerged macrophyte and a relatively strong correlation between nutrient and epiphyte. |
