Abstract: Hoagland's solution of water culture medium was used to study the effect of CO2 elevated on nitrate metabolism of wheat under normally natural light and light-shaded conditions. NO3--N, NH4+-N, nitrate reductase activity, total uptake N by wheat plants during solution cultural period and total N in plants were determined for comprehensive evaluation of the effect. Results showed that under both natural light and light-shaded conditions, addition of CO2 increased NO3--N uptake and its assimilative capabilities by plants. However, there were some difference between shoots and roots. With increase of CO2 concentration, the concentration of NO3--N and NH4+-N as well as nitrate reductase activity all decreased in shoots while the difference was not so distinct in roots, and the nitrate reductase activity did not decrease, but increase. Since NO3--N uptake by plants from the solution and the total N in plants were much enhanced by CO2 addition, it may be concluded that addition of CO2 has resulted in rise of nitrate absorption, assimilation and metabolism of wheat.

Key words: CO2 concentration, Winter wheat, Water culture, Nitrogen metabolism