Studies Of The Effects Of Carbon Dioxide On Cu/Zn Uptake By Indian Mustard & Sunflower

Soil is one of the most important natural resources that people depend on. With the development of economy, soils contaninated with heavy metals become an increasingly serious social problem. However, there are few technologies, which can decontaminate metal contaminated soil cost-effectively and efficiently. Remediation of soil by conventional engineering techniques often costs much money and can not afford large-scale practices. More importantly, it often results in destruction of the soil structure, decrease of the activities of soil- organism, and degradation of soil fertility. More than 400 species of~ metal- h~eraccumulating plants were found, since Brooks first proposed the concept 揾yperaccumulation? Hyperaccumulators may be useful for phytoremediation of heavy metal contaminated soils. This is so called phytoremediation technique. However most known hyporaccumulator plants have low biomass and/or slow growth rates, which make phytoremediation work inefficiently, and become a bottleneck problem among all-limiting factors. To overcome these limitations, it is necessary to develop new methods and techniques for phytoremediation. The effects of carbon dioxide on the boimass, Cu/Zn uptake by Sunflower and Indian mustard grown in sdil or nutrient solutions containing different Cu/Zn concentrations were studied in the present thesis. Two levels of CO2 treatments were used in homemade close CO2 chambers. After short-term and large numbers of experiments, following result were obtained. 1. It was found that enriching CO2 promoted growth and development of plants. It was also observed in our experiments that increasing CO2 concentration can shorten phenophase. For Cu control, the anthesis of Indian mustard exposed to CO2 concentrations of 800 and l200ppm is ahead of two and three days, respectively as compared to 35Oppm. Fertilizing plants with CO2 can promote development of new leaves, increase leaf numbers, and speed up biomass VI N~ (Ab~act) accumulation of plants, especially above ground biomass. For Cu control, the aboveground weight of sunflower rosed by 4.46% and 9.19%, and Indian mustard to 3 1.70% and 53.62%, respectively for pots grown under the CO2 concentrations of 800 and l200ppm as compared to 3SOppm. When grown under CO2 concentrations of 800 and l200ppm, plants showed an increase of growth rate by 48.09% and 73.52%, r~spcctively for Indian mustard, and 5.84% and 24.72% respectively for sunflower, at 100mg/Kg Cu in soil. When soil contained 200mg/Kg Cu, the aboveground growth rate of sunflower was from 8 1.70% to 148.75%, and Indian mustard from 6.19% to 80.33%, correspondingly. 2. Significant increases in Cu accumulation by sunflower and Indian mustard occurred with CO2 fertilization. Under CO2 concentration of SOOppm and Cu concentration of 100mg/Kg, the mean concentration in stems and leaves of Cu reached the maximum of l626mgCu/Kg dry weight in stems, 2539mgCu/Kg dry weight in leaves of sunflower, and 13696mgCu/Kg dry weight in stems, 4589mgCuIKg dry weight in leaves of Indian mustard, respectively in the case of pot experiment. However, for plants grown in nutrient solution, maximum Cu concentration in stems and leaves of sunflower was: 84mg/Kg dry weight and 63mg/Kg dry weight, respectively, at SOOppm CO2 and 2mg/...