Electron cytochemical analysis ofChlamydomonas polysaccharides

Conventionally prepared thin sections ofChlamydomonas reinhardtii grown photosynthetically or grown on acetate in the dark showed a pyrenoid surrounded by starch plates located centrally within the chloroplast. Light-grown cells contained few additional granules, whereas dark-grown cells had numerous large deposits. The PATAg technique of Thiéry was used to study the chemical nature of these deposits. Dense silver deposition was observed over the granules and plates in both types of cells; dark-grown cells had numerous, large areas of PATAg-reactive material. Other regions of the cells did not have reactive material. Enzymatic digestion with amylases showed that most, but not all, of the PATAg-reactive material was starch. Several small, granular areas remained in both light and dark-grown cells, even after extensive digestion. These results show that growth conditions affect patterns of starch storage and thatChlamydomonas has amylase-insensitive carbohydrate-containing material as well.