¹⁴CO₂ Fixation and Compartmentation of Carbon Metabolism in a Recombined Chloroplast‐ ‘Cytoplasm’ System

The Compartmentation of 14 CO 2 fixation and concomitant metabolism of l4 C‐iabelled products in a recombined system, composed of isolated intact spinach ( Spinacia oleracea ) chloroplasls and a ‘cytoplasm’ fraction, has been studied. Addition of ‘cytoplasm’ to chloroplasts fixing 14 CO 2 increased the label in hexoae monophosphates outside the chloroplasts at the expense of excreted dihydroxyacetone phosphate. The label in ammo acids was increased both inside and outside the chloroplasts. The results support the view that chloroplasls are not able to make 2‐oxoacids for amino acid synthesis directly from fixed CO 2 , but have to co‐operate with the cytoplasm and other organelles. The results also show that recombined systems can be useful for studies on the compartmen tation of carbon metabolism in pholosynthesizing plant tissues.