Starch Synthesis Studies in Zea mays: II. Molecular Distribution of Radioactivity in Starch.

The amylose and amylopectin fractions from kernel starch synthesized shortly after exposure of intact Zea mays L. plants to (14)CO(2) had similar specific radioactivities (counts per min per mg of carbohydrate). In both fractions the radioactivity was distributed throughout the molecules. These data are consistent with a model in which the polysaccharides are synthesized in the matrix of the amyloplast followed by crystallization of the completed molecules onto the starch granule.