On the Quantum Efficiency of Photosynthesis

For the maximum quantum efficiency of photosynthesis in green plants, the value ¼, which was obtained by Warburg and Negelein, has been generally accepted. However this value has appeared to be less certain since only much smaller efficiencies have been observed in recent experiments employing different methods. Because the theoretical aspect of photosynthesis greatly depends upon the maximum quantum efficiency, it is important that additional experiments be made. As a first step toward the solution of this problem, Warburg and Negelein's experiments have been repeated. When their methods are followed closely, a maximum efficiency of 1/4.2 is observed, which is in good agreement with their value. The remaining question— whether this method actually gives the over‐all efficiency for the assimilation of CO₂ under favorable conditions, or merely the efficiency for the reduction of a respiration product intermediate between CO₂ and carbohydrate—is not answered by these experiments. Further experiments along this line are in progress.