Relationship between age of culture and occurrence of the pigments of photosystem II of photosynthesis in heterocysts of a blue-green alga.

Microspectrophotometric examination of the pigments in vivo of heterocysts of Anabaena sp. L-31 has shown that most heterocysts of 2-day-old cultures possess only very small amounts, if any, of c-phycocyanin, allo-phycocyanin, and c-phycoerythrin, the main pigments comprising photosystem II of photosynthesis. The quantities of these pigments, however, increase with age of cultures, and by the end of 5 days the majority of heterocysts contain comparatively large amounts. The culmination of this sequential development is observed in most heterocysts of 7- to 15-day-old cultures when the full complement of photosystem II pigments is present. The spectral characteristics at this stage are similar to those of vegetative cells and suggest a dedifferentiation of heterocysts.