Effects of blue light on respiration and carbon dioxide fixation in colorless Chlorella mutant cells

A colorless mutant of Chlorella vulgaris (Mutant #125) starvedin darkness, showed suppressed rates of respiration and darkCO₂ fixation, which were significantly recovered by illuminationwith blue light. The main CO₂ fixation product under blue lightwas aspartate. Such enhancements did not take place in cellsactively growing in the glucose medium. Both enhancing effectsof blue light (456 nm) were saturated at light intensities aslow as 400–800 erg.cm^-2.sec^-1. The action spectra forthese enhancing effects were similar to each other; both showedpeaks at 460 nm and 380 nm, which correspond to the absorptionmaxima of flavin. All these findings indicate that the samemechanism underlies the observed effects of blue light on CO₂fixation and respiration. The role of blue light which bringsabout the enhancements in CO₂ fixation and respiration is discussed. (Received June 1, 1974; )