Effect of reduction of the light collecting complex on the size of the photosynthetic unit and the number of reaction centres of photosystems in chlamydomonas reinhardii mutants

The values of the photosynthetic units and the numbers of reaction centres (r.c.) of photosystem I (p.s.-I) and photosystem II (p.s.-II) calculated from the photoinduced changes in the absorption of pheophytin, P₆₈₀ and P₇₀₀ and also the e.s.r. signals I and II have been investigated. It was established that in the course of reduction of the light collecting complex (l.c.c.) in the mutants the size of the photosynthetic unit falls and amounts per r.c. of p.s.-I to about 120±20 and of p.s.-II to 50±10 chlorphyll a molecules. On conversion to 1 mg of chlorophyll the number of r.c. in the mutants containing p.s.-I rises 5 fold and p.s.-II 10-20 fold. It is concluded that the mutants ACC-11, ACC-14 and ACC-42 as well as p.s.-I contain part of the l.c.c., while the mutants ACC-66, ACC-98, ACC-100 and ACC-238 form only the p.s.-II complex. Regardless of the degree of reduction of the l.c.c. the number of r.c. of the photosystems in the chloroplasts of the mutants does not change significantly.