| Summary: | 博士 === 中興大學 === 森林學系所 === 95 === This study investigated the effects of different carbon dioxide concentrations (354.29±12.80 μL L-1, Ambient, A, or 719.65±28.70 μL L-1, Elevated, E) and different nitrogen concentrations (112, 224 or 448 ppm) on growth performances, gas exchange, ability of radiation capture, allocations of non-structural carbohydrates and nitrogen nutrients, situations of pH and nitrogen nutrients, and the role of plasma membrane H+-ATPase played on nitrogen uptake in the soil medium of Cinnamomum camphora seedlings for eight weeks. During entire experimental period, the net height growth and net ground diameter growth were continually and significantly enhanced by elevated carbon dioxide concentration, but have no obviously difference among nitrogen concentrations. Although photosynthetic rate was promoted by elevated carbon dioxide concentration and higher nitrogen concentration after four weeks, the results from chlorophyll fluorescence measurements and chlorophyll contents have demonstrated that the light reaction of photosynthesis has been negatively affected by elevated carbon dioxide concentration. This impact would be weak with nitrogen concentrations increased. After eight weeks, photosynthetic rate has gradually acclimated under elevated carbon dioxide condition. Chlorophyll fluorescence parameters and chlorophyll contents of elevated carbon dioxide treatment have no significantly different from those of ambient treatment. Because of it has a tendency to transport more carbon to the roots, and to improve nitrogen uptake. Plasma membrane H+-ATPase could accelerate nitrogen uptake, especially for nitrate uptake. But nitrate assimilation has a trend to decrease in the shoots and to increase in the roots under elevated carbon dioxide condition. According to the results from nitrate and ammonium contents of roots, pH value and nitrate and ammonium contents of soil medium, I may conjecture that the hobby for nitrogen forms to uptake has changed, from nitrate uptake changed to ammonium uptake. Nitrogen concentration supply adequately or not would have a positive effect on growth performances, physiology, the light reaction of photosynthesis, allocations of carbon and nitrogen between shoots and roots and nitrogen absorption to response carbon dioxide concentration enrichment.
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