When ammonia was added to cells ofChlorellawhich had fixed14CO2photo synthetically,14C which had been incorporated into starch was greatly decreased. A similar effect was observed when potassium nitrate and sodium nitrite were added. The ammonia-induced decrease in14C-starch was observed in all species ofChlorellatested. With cells ofC. vulgaris11h, most of the radioactivity in starch was recovered in sucrose, indicating that ammonia induces the conversion of starch into sucrose. The percent of14C recovered in sucrose differed from species to species and practically no recovery in sucrose was observed inC. pyrenoidosa. In most species tested, the enhancing effects of blue light and ammonia on O2uptake as well as the ammonia effect on starch degradation were greater in cells which had been starved in phosphate medium in the dark than in non-starved cells. In contrast, the enhancing effect of ammonia on dark CO2fixation was much greater in non-starved cells.C. pyrenoidosawas unique in that blue light did not show any effect on its O2uptake.
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