Research On Response For Lead Stress Of Commelinaceae Plants

Commliaceae plants have a good application prospect on plant arrangement with characters of widely distributed, strong adaptability, concealment resistance. Many kinds of commliaceae plants are cultured in garden as ornamental garden foliage plants. Many articles report the beauty of commliaceae plants and their application on landscape construction. However, few studies have been reported so far on phytoremediation of lead pollution. Therefore, several ornamental commliaceae plants were used as research object in this experiment. Trough method of water culture,1/4 Hoagland nutrient solution with different Pb concentrations were used as medium to cultivate the commliaceae plants in artificial simulation experiment under Pb stress. Lead's propensity to accumulate of commliaceae plants and their change of growth and physiology characteristics under Pb stress were studied in this dissertation.The lead tolerance plants were screened from sample materials by step test under 0-1000 mg·L-1 concentrations of Pb stress. Subsequently, the Pb enrichment characterize, growth changes and physiology characterize of the chosen plants were studied by further artificial simulation experiment under 0-2000 mg·L-1 concentrations of Pb stress. The main contents and consequence of this thesis are as follows:1. Through investigating the distribution of commliaceae plants in Sichuan, six appreciation plants were chosen as experiment materials for choosing the lead resistant species. The result shows that under 1000 mg·L-1 concentrations of Pb, Tradescantia sillamontana and Setcreasea purpurea and Commelina communis from the selecting commliaceae plants materials are still alive and display better lead resistance.2. The Pb enrichment characterize, growth changes and physiology characterize of Tradescantia sillamontana and Setcreasea purpurea have been further studied in the artificial simulation experiment under 0-2000 mg·L-1 concentrations of Pb stress by considering factors of ornamental value, garden application, bigger biomass and so on.3. The data of lead contents in Tradescantia sillamontana and Setcreasea purpurea show that both of them have the capability of accumulating Pb in some extent. Tradescantia sillamontana has stronger ability of lead metastasis (coefficient is bigger than 1), and both the contents of Pb in its above-ground part and root can reached above 1000mg·kg-1. For Setcreasea purpurea, the lead are mainly enriched in its well developed root system, the contents of Pb reach above 1000 mg·kg-1 as well. But there are small amount of lead in its above-ground part, the maximum value of accumulated lead is about 500 mg·kg-1.4. The determination of growth indexes shows that while the concentration of Pb reaches 500 mg·L-1, both the growth situations of Tradescantia sillamontana and Setcreasea purpurea are restrained. Else, as the concentration of Pb rise gradually, the green leaves of them are decreased and their height growth are slowed down. Furthermore, their fresh weight of above-ground part and root are declined sharply. But some Tradescantia sillamontana and Setcreasea purpurea only die at 2000 mg·L-1 Pb concentrations, which is showed that both of them have the capability of higher tolerance for lead stress.5. The measurement results of some typical stress physiology about Tradescantia sillamontana and Setcreasea purpurea show that the chlorophyll contents increase first and then decrease, the contents of chlorophyll a has a bigger change than chlorophyll b as the concentration of Pb rise gradually. Also their relative conductivities and malonaldehyde contents rise gradually, and the correlativity between them reaches the significance levels. Meanwhile, the content of proine and activity of peroxidase about Tradescantia sillamontana and Setcreasea purpurea also raise first and then decrease, but the changes of nitrate reductase activity have a big difference. The nitrate reductase activities of Tradescantia sillamontana reduce little by little. As for Setcreasea purpurea, the activities of nitrate reductase increase first and then decrease as well.