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

Abstract

ble amino acids. Bassham et al. (2) presented evidence for the conversion of amino acids of the active tturning-over free pools to the protein bound amino acids during photosynthesis in Chlorella. However, they also observed that the rate of flow of Cl4 through the free amino acid pools was much greater than the rate of movement of carbon inlto proteins. anid they were forced to consider the possibility of the free amino acids being used in part for the synthesis of nonnitrogenious comipounds. In a previous paper we have showni that light induces a rapid turnover of the amiino acid pools in the chloroplasts of tobacco leaves and that this effect is centered primarily around serine which tends to be metabolized rapidly in the light but remains fairly stable in the dark (9). It was further shown that in tobacco leaves the label from the amino acids went chiefly into starch rather than into protein. Tolbert and coworkers (7), and Wang and Burris (13) studied the fate of serine that was fed to leaves and found that in the light serine was converted into sucrose. The present conmmunication deals with the incorl)oration of early labeled *amino acids into leaf protein when leaves are fed C140, and the effect of light and dark, on the penetration of serine into chloroplasts, and the metabolism of serine fed to leaves.