COMPARATIVE STUDIES OF PHOTOSYNTHESIS IN NOSTOC MUSCORUM AND CHLORELLA PYRENOIDOSA

Abstract

Methods are described for the continuous culturing of Nostoc muscorum and for the manometric measurement of its photosynthesis. N. muscorum required a more dilute and more alkaline medium for growth and for measurement of its photosynthesis than Chlorella pyrenoidosa. Although lacking organized chloroplasts, N. muscorum exhibited higher photosynthetic capacity at 25 °C. in terms of cell numbers and chlorophyll content than C. pyrenoidosa. The photosynthetic capacities of N. muscorum and C. pyrenoidosa were not significantly different on a solids basis. Saturating light intensities, optimum and maximum temperatures, activation energies, induction periods, and inhibition by phenylurethane were similar for photosynthesis in Nostoc and Chlorella. Aerobic induction was not abolished by an atmosphere of pure oxygen, or by glucose feeding.Photosynthesis in Nostoc was abolished by exposing the filaments to weakly acidic media, and usually was injured by washing them with neutral or mildly alkaline potassium-free media. The lyotropic series for the prevention of washing injury in Nostoc was K> Rb> NH4, Li, Na. This washing effect is discussed in relation to the chloride effect on the Hill reaction, the magnesium effect on Azotobacter respiration, as well as the effect of potassium on the bioelectric properties of Nitella, to which it appears related.