Ultrastructural Study of Haematococcus lacustris (Girod.) Rostafinski (Volvocales)

I. Some aspects of carotenogenesis

Abstract

The process of accumulation of secondary carotenoids (astaxanthin) in Haematococcus lacustris was analysed in the optical and electron microscopes. The more relevant results of this cytological study are the following: a. In motile cells, the lipochromes are spherical inclusions, initially of small size, and located in the perinuclear cytoplasm apparently in preferential correlation with E. R. Although without a true limiting biomembrane, these sudanophilic and osmiophilic inclusions do not easily fuse when contacting. b. In the cysts, the pigment deposits, although being identical to the ones of the motile cells in what concerns their location and affinity for lipids “stains”, show a variety of shapes, including “long filaments”, rods and more or less complex reticulate forms. c. Cells of the older cultures (11-20 days) appear almost uniformly “stained” deep red. This process is reversible, i.e., these cultures again turn green when successively subcultured to fresh media. d. Apart from the stigma globules, the haematochrome is always localized outside the chloroplast, the photosynthetic apparatus of which remains practically intact through this process. Then, no sign of plastidal transformation, (chloroplast in chromoplast) comparable to the changes which take place in various organs of higher plants was observed.