uptake in the dark, if the chloroplasts are first given a pre-illumination period necessary to establish ATPase conditions*. Thus ATP-dependent Ca uptake occurs in both chloroplasts and mitochondria in the absence of electron flow. Chloroplasts have not as yet been found to drive Ca uptake under conditions of electron transport only, as occurs in mitochondria.
Chloroplast ion uptake shows a remarkable similarity in chemical requirements to the corresponding process which has been described for mitochondriaV, s. Little is known of the factors that control the ionic composition of chloroplasts. SALTMAN, FORTE AND FORTE 9 reported that the monovalent cation composition of chloroplasts differs from the cytoplasm in the blue green algae Nitella. Also, JAGENDORF AND HIND 5 have reported light-induced pH changes that are related to phosphorylation in spinach chloroplasts. Besides the light-dependent ion uptake reported here, spinach chloroplasts also manifest a light-induced shrinkage 2, z0 Thus the light-induced movement of water and ions in chloroplasts may play a significant role in establishing the ionic relationships of chloroplast-containing plant cells.