Ornamental Emergent Plants And Their Use Potential In Yangzhou Area

The development of cities has been seriously prevented because of the ill use of landscape plants and water eutrophication. So it is imminent to exploit and utilize the local resources of ornamental plants properly and to solve the problem of water eutrophication. In this paper, we investigated and screened the local resources of ornamental emergent plants in Yangzhou area. Meanwhile, three emergent plants, Monochoria vaginalis, Ammannia baccifera and Sagittaria pygmaea were chosen as experimental materials to examine the effects of different concentration nitrogen on them and their capabilities of removing nitrogen.The main results are showed as follows:1. In Yangzhou area, it was very rich in emergent plant resources which contain about 92 most common species belonging to 62 genera of 28 families. Obviously, Cyperaceae, Poaceae and Polygonacae were the top three families that contributed greatly to the emergent plants. Typha angustifolia, Phragmites austrails and Alternanthera philoxeroid.es etc.17 species plants widely distributed in the wetland plant communities and often served as dominants.2. As the results of ethnobotanical and other evaluation methods, Typha angustifolia, Acorus calamus, Scirpus validus, Alisma plantago-aquatica, Sagittaria trifolia etc.20 species indigenous plants which were seldom or never used in the construction of urban landscapes had the high comprehensive use value. At individual level, Typha angustifolia, Monochoria vaginalis, Ludwigia octovalvis, Ranunculus sceleratus, Colocasia esculenta, Sagittaria trifolia etc. had the higher composite salience value based on ornamental value. However, Polygonum japonicum, Typha angustifolia, Scirpus validus, Sagittaria pygmaea, Colocasia esculenta, Cyperus glomeratus etc. owned the higher rank at population level.3. The effects of nitrogen on the emergent plants were not only related to the concentration of nitrogen, but also to plant species. Nitrogen had significant effects on biomass, root length, and root activity of the three tested emergent plants. At the end of experiments, nitrogen had no significant effects on the dry weight of M. vaginalis and S. pygmaea, but high concentration nitrogen significantly inhibited their water content. Nitrogen could significantly inhibit the water content of A. baccifera, but the higher concentration nitrogen could improve its dry weight significantly. The root length and root activity of M. vaginalis in treatment groups was significantly lower than those of control, but it showed no significant difference for A. baccifera and S. pygmaea.4. After the treatment with different concentration nitrogen for 10 days, when the concentration was≥44 mg/L, nitrogen would significantly inhibit the content of chlorophyll in M. vaginalis; when the concentration was≥86 mg/L, nitrogen could also inhibit the content of chlorophyll significantly in S. pygmaea. However, nitrogen would increase the content of chlorophyll significantly in A. baccifera when the concentration was≥23 mg/L.5. After the treatment with different concentration nitrogen for 10 days, the activity of SOD, CAT and POD for the three emergent plants were significantly impacted. Nitrogen could significantly increase the activity of SOD in both M. vaginalis and S. pygmaea when the concentration≥86 mg/L; when the concentration≥7.25 mg/L or≥12.5 mg/L, nitrogen could significantly reduce the activity of CAT in S. pygmaea and M. vaginalis respectively; When the concentration≥7.25 mg/L, nitrogen could significantly inhibit the activity of POD in M. vaginalis, but showed a increasing impact on A. baccifera. Nitrogen could significantly increase the content of MDA in M. vaginalis when the concentration was≥44 mg/L, but no significant effect on the content of MDA in S. pygmaea and A. baccifera for all nitrogen concentration.6. All the three emergent plants showed capacities of removing nitrogen in the environment. There was a negative relationship between the capacity of removing nitrogen and nitrogen concentration. A. baccifera had a high capacity of removing nitrogen under the condition of lower nitrogen concentration, but conversely for M. vaginalis; S. pygmaea showed a higher capacity of removing nitrogen under the condition of higher nitrogen concentration.7. Nitrogen had little effects on pH value but significant effects on the electronic conductivity of culture medium. The electronic conductivity of culture medium showed a rising tendency with the increase of nitrogen concentration. During the experiment, the pH value showed a tendency of falling down for all three emergent plants. But it was more significant for A. baccifera compared with the other two plants. For M. vaginalis, The electronic conductivity of culture medium showed a tendency of rising, but it showed a obvious tendency of falling down for both A. baccifera and S. pygmaea.Base on the results showed above, we can conclude that indigenous emergent plants have higher potential in the construction of urban landscapes. Nitrogen can affect the vegetative growth of some emergent plants by affecting their root activity, water content and photosynthesis. Meanwhile, nitrogen can also change the activity of antioxidase, the content of MDA and total nitrogen of plants. Emergent plants also show higher potential of removing nitrogen in the environment.