The regreening of nitrogen-deficientChlorella fusca

The wildtype strain 211-15 of the green algaChlorella fusca appears orange after long incubation in nitrogen-sparse media. The cells regreen within 24 h when incubated in a nitrogen-rich medium in the light. During the regreening process the very low chlorophyll a: b ratio of 1.8 is increased to 3.3 indicating a preferential synthesis of chlorophyll a. Respiratory activity of the cells is high throughout the regreening period. Photosynthetic oxygen evolution occurs 4–6 h after the commencement of regreening. When regreening is completed under the defined conditions synchronized cell division occurs.