[The size of the photosynthetic unit and its variability : II. The role of the carotenoids in energy transfer during photosynthesis in a Chlorella mutant].

Even under unsaturated conditions of light a yellow green Chlorella mutant shows a higher photosynthetic efficiency than the normal form on the basis of chlorophyll. This difference in photosynthesis is not influenced by irradiation with red light although in the mutant the ratio carotenoids:chlorophyll is four times higher than in the normal green cells. Therefore we conclude that in the mutant the efficiency of excitation transfer from carotenoids to chlorophyll is reduced. As a result of the smaller photosynthetic units fewer carotenoid molecules are in the vicinity of the chlorophyll. The average increase in the distance between the molecules of the two pigment groups results in the reduction of the excitation transfer to chlorophyll.