| Abstract | Tracer techniques have been used to examine the pattern by which the straight-chain and branched components of wheat starch are laid down in the maturing kernel. The starches were isolated from kernels of wheat plants to which had been administered glucose-1-C¹⁴, acetate-1-C¹⁴, or acetate-2-C¹⁴ at different periods of active growth under field conditions. Fractionation of the starches gave amylose and amylopectin and, in addition, a minor fraction of amylopectin, all labelled with carbon-14. Notable differences were found in the specific activity of these starch fractions, and in the distribution of carbon-14 within the monomeric units of samples labelled via glucose-1-C¹⁴. These findings indicate that the process of starch deposition in the kernel is not extensively reversible. Amylopectin appears to be formed from amylose, in agreement with current views, and it is suggested that the minor amylopectin component is an intermediate in this conversion process. |
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