Some Remarks on the Photosynthesis of Green

Of recent years there have been considerable contributions to the literature of the photosynthesis in plants. One must mention here the papers of Franck (1) and Stoll (2), who developed the theory proposed by Willst~tter (3), the interesting considerations of van Niel and Miiller (4), and the detailed discussions by Gaffron and Wohl (5) and Emerson (6). The most important of recent experimental discoveries in this field is the "photosynthetic unit" of Emerson and Arnold (7). These authors have shown that only a small fraction, about 1/2000, of the total amount of chlorophyll present takes part directly in the assimilation process. I t seems that the chlorophyll is entering into photosynthesis only in certain photosynthetic units containing a few hundred molecules. Gaffron and Wohl (S) also concluded from the previous assimilation experiments of Willstittter and Stoll (8) that about 1000 chlorophyll molecules must cooperate to bring about the reduction of one molecule of CO2, during the experimentally determined time of the "Blackmail period." Another important point is the rSle of iron in the assimilation of green plants. Although the need for iron in the photosynthesis of green plants has been known for a long time and the presence of iron in the chloroplasts was established by Moore (9) yet the rSle of iron has not been considered in the modern theories. I t is not only that the plants grown in the absence of iron remain pale or colorless (chlorosis) and therefore show a low photosynthetic activity due to their 501