EUGLENA GRACILIS IN SYNCHRONOUS DIVISION. II. BIOSYNTHETIC RATES OVER THE LIFE CYCLE

¹ Department of Zoology, University of California, Los Angeles 24, California

1. When grown autotrophically on an appropriate light-dark regimen, populations of the flagellate Euglena gracilis divide synchronously, an approximate doubling of cell number occurring in each dark period.

2. Growth of the average cell during the light period, which is essentially devoid of cell divisions, is described in terms of dry mass, total protein, DNA, RNA, chlorophyll a, and the carotenoids. The average Euglena duplicates all of these constituents in each light period.

3. Dry mass, volume, RNA, and probably DNA of the average cell increase to a doubling in a linear fashion over the whole of the 16-hour light period.

4. The photosynthetic pigments chlorophyll a and the carotenoids (beta-carotene) increase at rates which do not deviate greatly from linearity.

5. Synthesis of total protein is completed 5 or 6 hours before termination of the 16-hour light period. It is inferred that storage products are synthesized at rates complementing protein synthesis in such a way that dry mass increases linearly.