Wavelength effects on photosynthetic carbon metabolism in Chlorella

To study the wavelength-effect on photosynthetic carbon metabolism,¹⁴C-bicarbon-ate was added to Chlorella vulgaris 1 lh suspensionunder monochromatic blue (456 nm) and red (660 nm) light. Thelight intensities were so adjusted that the rates of ¹⁴CO₂ fixationunder blue and red light were practically equal. Analysis of¹⁴C-fixation products revealed that the rates of ¹⁴CO₂ incorporationinto sucrose and starch were greater under red light than underblue light, while blue light specifically enhanced ¹⁴CO₂ incorporationinto alanine, aspartate, glutamate, glutamine, malate, citrate,lipid fraction and alcohol-water insoluble non-carbohydratefraction. Pretreatment of the algal cells in phosphate mediumin the dark, which was essential for the blue light enhancementof PEP carboxylase activity, was not necessary to induce theabove wavelength effects. Superimposition of monochromatic bluelight at low intensity (450 erg.cm^–2.sec^–1) on thered light at saturating intensity caused a significant decreasein the rate of ¹⁴CO₂ incorporation into sucrose and increasein incorporation into alanine, lipid-fraction, aspartate andother related compounds, indicating that the path of carbonin photosynthesis is regulated by short wavelengdi light ofvery low intensity. Possible effects of wavelength regulationof photosynthetic carbon metabolism in algal cells are discussed. ¹ Part of this investigation was reported at the XII InternationalBotanical Congress, Leningrad, 1975 and the Japan-US CooperativeScience Seminar "Biological Solar Energy Conversion", Miami,1976. Requests for reprints should be addressed to S. Miyachi,Radioisotope Centre, University of Tokyo, Bunkyo-ku, Tokyo 113,Japan. ⁴ Present address: Department of Chemistry, Faculty of PharmaceuticalSciences, Teikyo Univ., Sagamiko, Kanagawa, Japan. (Received August 6, 1977; )