Effect of Carbon Dioxide Concentrations on Dry Matter Accumulation in Bean Leave Measured by an Improved Half-leaf Method

Photosynthetic activity in the attached leaf of bean at different CO_2 concentrations under day light was investigated using the improved half-leaf method. About 14 mg dry matter/dm^2/hr. which correspond to about 23 mg CO_2/dm^2/hr. (assuming 1 mg CO_2=0.61mg dry matter) at normal atmospheric CO_2 concentration was estimated. More increased rate was obtained with high CO_2 concentrations and the maximum rate was usually found at 1,500 ppm of CO_2 in the most of the experiments regardless of different leaf age, leaf position and high nitrogen treatment. However, no effect of high CO_2 concentration on translocative rate was observed in the present investigation. Diurnal changes of photosynthesis and translocation were also investigated using the same method. Photosynthetic rate increased to a maximum until noon and then decreased till late afternoon, and translocative outflow was approximately parallel with increasing photosynthetic activity