NUTRITIONAL CONTROL OF CELL PIGMENTATION IN CHLORELLA PROTOTHECOIDES WITH SPECIAL REFERENCE TO THE DEGENERATION OF CHLOROPLAST INDUCED BY GLUCOSE1

Abstract

1. Measuring the chlorophyll contents and growth of the algal cells grown in media containing different amounts of glucose (G) and urea fas a nitrogen source, N), it was found that the ratio N/G determines pigmentation of the cells (colourless, yellow, yellowish green and green) under the experimental conditions used, and thus a sort of colour map of the differently pigmented cells was obtained. 2. The bleached cells produced at lower N/G ratios and the green cells obtained at higher ratios could he cultured successively under heterotrophic and photoautotrophic conditions, respectively, and both forms were interconvertible on transferring each cell type into a new medium having appropriate N/G ratio. 3. Studies on these bleaching and greening processes under different experimental conditions revealed that the greening requires essentially the supply of N-sources—no strict specificity was observed with different N-sources tested—as well as light, but can take place independently of growth, while the bleaching is caused most strongly by glucose (and fructose) among the carbon sources examined and proceeds essentially independent of light. 4. The bleaching effect of glucose at its higher concentrations is primarily due to its degradation effect on chloroplast structures including lamellae. This effect of glucose is markedly diminished at its decreasing concentrations and is also counteracted by the supply of N-source (urea) of higher concentrations.