Synthesis of Organic Nitrogen and Chlorophyll by Nitzschia Closterium

Abstract

Experiments have been made with the marine diatom Nitzschia closterium grown in artificial light with different nitrogen sources.After the nitrogen source in the medium was exhausted, photosynthesis and cell division continued, the cells becoming nitrogen- and chlorophylldeficient.On adding a nitrogen source to deficient cells and storing in darkness, synthesis of organic nitrogen, mostly water soluble, proceeded rapidly from ammonium, less rapidly from nitrate and very slowly from nitrite, with which it grows in light as rapidly as with nitrate or ammonium nitrogen.Possible reasons why nitrate but not nitrite is reduced in the dark are discussed.Chlorophyll and yellow pigments were synthesized in the dark by nitrogendeficient cells in quantity related to the organic nitrogen synthesized.Chlorophyll was synthesized in small amount by non-deficient cells which had been growing rapidly before transfer to darkness. Cells contained less chlorophyll when grown in moderately bright than when grown in dim light.