PHOTOSYNTHESIS IN CELL DEVELOPMENT.

Abstract

Abstract Non-synchronized suspensions of the green, high-temperature alga Chlorella 7-11-05 were subjected to fractional centrifugation, and two size groups of cells were separated. The small-cell fraction was presumed to consist largely of younger cells and the large-cell fraction predominantly of older cells. Manometric measurements in phosphate buffer at pH 4.5, in bicarbonate buffer at neutral pH, and in carbonate-bicarbonate buffer at pH 9.3 indicated that younger cells invariably possessed higher photosynthetic activity than older cells, provided the separation of cells into size fractions was reasonably good and the large cells were prevented from dividing during the process of separation. The superior activity of younger cells was ascertained at various light intensities and at different temperatures. Previous observations on the decline in photosynthetic activity with the age of synchronized cells were thus substantiated in the absence of a synchronizing agent, and the decline in photosynthetic capacity must be assumed to be characteristic of normal cell development. The decline in metabolic activity in the course of cell development is discussed in connection with metabolic turnover and is viewed as a demonstration of aging of cells.