Effect of Light on the Incorporation of Serine into the Carbohydrates of Chloroplasts and Nonchloroplast Fractions of Tobacco Leaves

Abstract

Glycine and serine constituted the bulk of the early labeled amino acids when tobacco leaves were fed Cl14O2 in the light. The glycine pool became saturated rapidly. In the light, C moved through the pools of these amino acids into carbohydrates, particularly sucrose and starch. Amino-acid incorporation into protein in the leaves studied was low, with the bulk of the protein 614 accounted for by protein-bound serine and glycine. Serine-3-C-C14 when fed to leaves moved rapidly into the chloroplasts as well as into the nonchloroplast parts of the leaf, but was rapidly metabolized only in the light. The major products of serine metabolism in the leaf in the light were sucrose and starch and some protein.