Effect of Light and Dark on the Intracellular Fate of Photosynthetic Products

Abstract

The usefulness of the nonaqueous method of isolating chloroplasts for a study of the intracellular fate of the early products of photosynthesis and a study of the pools of various metabolites located inside and outside of the chloroplasts was demonstrated. The existence of very rapidly labeled pools of glycine, serine, alanine, and glycolic acid as well as phosphorylated compounds in the chloroplasts of tobacco leaves was demonstrated. Serine appeared to move freely through the chloroplast membrane while the membrane was less permeable to certain phosphorylated compounds. Light induced a rapid turnover in the amino-acid pools, with C moving from them into carbohydrates, particularly starch. This effect resulted chiefly from the rapid metabolism of serine in the light but not in the dark. The results presented are in agreement with the suggestion that the glycolate pathway from early C products of photosynthesis to carbohydrates is operative in tobacco leaves.