Aspects of metabolic development in an illuminated synchronous culture of Scenedesmus obtusiusculus

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Abstract
Developing synchronous cells of Scenedesmus obtusiusculus Chod. were investigated during the 15-h light period of the 24-h life cycle. Measurements were made of photosynthesis and of the chlorophyll, carotene, nucleic acid, and protein content, including intracellular phosphorus.Photosynthetic oxygen evolution (μmol/mg chlorophyll) increased during the early growing stage and declined gradually in the older cells. Chlorophyll, carotene, protein, ribonucleic acid, and ribonucleic acid phosphate of these cells increased during the growth phase (dry weight basis) and declined in the sporulating phase, whereas the deoxyribonucleic acid and deoxyribonucleic phosphate decreased during the growth phase. Deoxyribonucleic acid increased slightly in the sporulating phase, but deoxyribonucleic acid phosphate remained relatively constant during this period. When calculated on a per cell basis, ribonucleic acid and ribonucleic acid phosphate increased steadily throughout the period of observation, whereas deoxyribonucleic acid and deoxyribonucleic acid phosphate remained constant during the first 5 h and then increased gradually. Analysis of the intracellular distribution of phosphorus(dry weight basis) revealed that methanol-soluble (lipid) phosphorus decreased steadily with cell growth, whereas the content of acid-soluble phosphorus and ethanol–ether-soluble (lipid) phosphorus fluctuated markedly. The pH of the culture medium increased concomitantly with cellular development during the light period.

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