The capacity for organic synthesis in cells of successive developmental stages

Summary

Synthesis of organic matter was studied on synchronized suspensions of the green high-temperature alga, Chlorella 7-11-05, in regard to the composition of the suspending fluid and the developmental status of cells. Rates of synthetic activity were determined as changes in optical density of algal populations. The validity of this technique was substantiated by special parallel measurements of changes in optical density, dry weight, and chlorophyll content of algal suspensions.

It was found that cells of earlier developmental stages generally possess a higher capacity for organic synthesis than cells approaching the end of the life cycle. Earlier reports on the decline in the photosynthetic capacity toward cell division, observed in such nitrogen-free media as phosphate, bicarbonate, and Warburg's No. 9 buffers, were thus substantiated by observations on the decline in organic synthesis in the course of cell development recorded in the same three, as well as in several other, nitrogen-free and nitrogen-containing media.

Vacillation of metabolic activity throughout the life cycle and in the course of measurements during one experiment was discussed, and a higher reliability of the time-course curves as compared with a set of data obtained for short-time intervals was ascertained. The regular sequence of changes in synthetic activity in the course of cell development was ascribed to the regularity of changes in the rates of the anabolic and catabolic moieties of the metabolic turnover.