Photosynthetic Reactions by Chloroplast Fragments of Chlamydomonas reinhardi.

Photosynthetic phosphorylation has been studied in (letail in a wxide variety of higher plants andl photosynthetic bacteria, but to date only a few investigations have been made in the algae. Although a high rate of photosynthetic phosphorylation has been reported for cell-free preparations of the blue-green alga A iabaena z,ariabilis (11), only fragmentary data are available describing this process in cell extracts of green algae ( 13, 6, 2). Repeated efforts in this laboratory faile(d to demonIostrate appreciable rates of photophosphorylationl by chloroplast fragments of the unicellular green alga, Chlamiy,doinonas reinhardi. Occasional positive results were dismissed because of the lack of repeatability. Recently Hughes et al. (4) (lemonstrated that pigmented particles of the photosynthetic bacterium. Chllorobimwst thiosulfatoph ilu in, isolated from cells growni under conditions of phosphate limitation. carrie(l out a light dependent esterification of Pi. However, particles isolated from cells grown in a phosphate buffered medium showed only an ADP dependent but light independent release of Pi, possibly froml polyplhosphate. For this reason, an investigation of photosynthetic phosphorylation in phosphate depleted cells of C. reinlhardi was undertaken. The present communication describes photosynthetic phosphorylation, in the presence of TPN, vitamin K., FMN, and PMS4 by chloroplast fragments isolated from these cells.