Photosynthetic oxygen production and the size of the photosynthetic unit in a cell-free preparation from Cyanidium caldarium

A cell-free preparation has been isolated from a mutant of Cyanidium caldarium, grown under conditions such that there is 15 times less chlorophyll per photosynthetic unit than in normal green algae. The preparation is sensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea and shows the well-characterized oscillation of O₂ yield, from saturating flashes, following a period of dark adaptation. Greening experiments with dark-grown, wild-type Cyanidium show that the synthesis of photosynthetic units precedes that of bulk chlorophyll and that the O₂-producing system is assembled before the total system coupled to CO₂. No large-scale cooperation of chlorophyll molecules is required for O₂ production.