Action Spectrum of Photosynthesis for Skeletonema costatum Obtained with Carbon‐14

The quantized action spectrum of photosynthesis for Skeletonema costatum was obtained from values of photosynthetic 14CO2 uptake at various wavelengths of light isolated “with a diffraction grating monochromator. The quantized action spectrum of photosynthesis exhibited maxima at wavelengths similar to maxima in the absorption spectrum, in vivo, of a suspension of S. costatum cells. While the 14CO2 technique will provide an accurate action spectrum of photosynthesis for diatoms, a large number of samples is required in order to minimize sampling error.