PHOTOREDUCTION BY CHLAMYDOMONAS

Abstract

termed by Gaffron (1940), who has studied this process in some detail particularly in Scenedesmus (Gaffron, 1945). This process has been shown to occur also in a number of other species of green, blue-green, and red algae (Frenkel and Rieger, 1951). Algae which can carry out either photoreduction or normal photosynthesis under appropriate conditions are of particular interest; since they permit investigators to compare the effects of various physical and chemical agents on two photosynthetic reactions in which metabolic pathways differ in certain important respects. From such studies, Gaffron (1945) has drawn important conclusions about the nature of the catalytic systems involved. Of the algae known to carry out photoreduction, Chlamydomonas proves to be more suitable in certain respects than Scenedesmus, particularly because its adaptation to a metabolism involving molecular hydrogen is much more rapid (Frenkel, 1952). MATERIALS AND METHODS.-They are essentially the same as the ones described in an earlier paper (Frenkel, 1952). It should be added that Chlamydomonas is more sensitive to extensive handling, exposure to heat or prolonged cold storage than a number of algae which have been used in photosynthetic research, such as Chlorella or Scenedesmus. In preparing algal suspensions for manometric studies it is advisable to centrifuge cells for only five to ten minutes in a cooled centrifuge (5-10C.) at no more than 1000 X g. They should not be centrifuged and resuspended more than twice. Liquid cultures cannot be stored in the refrigerator for more than a few hours without considerable loss of photosynthetic activity. Agar slants can be stored for several weeks in a refrigerator with only