THE COMPOSITION OF STARCH GRANULES FROM DEVELOPING BARLEY GENOTYPES

Starch, nitrogen and phosphorus were assayed in samples from isogenic lines — Glacier (normal) CI9676, Glacier (high amylose) Ac 38, Oderbrucker (normal) and Waxy Oderbrucker (low amylose) — which were harvested at intervals from 14 days after anthesis (DAA) to grain maturity. Quantitative determination of the size distribution of the starch granules was carried out using a Coulter counter with 100-channel analyser and the number of A- and B-granules per endosperm calculated. Large and small starch granules were separated by differential sedimentation in water. In each of the four lines there was a different linear relationship between the increasing amylose content and the increasing phosphorus content of the large granules during grain development. Small amounts of amylose were found in the large A-granules of the variety Waxy Oderbrucker, but none was detected in the small B-granules. It was concluded that the data for non-waxy A-granule starches were compatible with a model in which there is a core of low-amylose low-lipid starch. The composition of the starch in the B-granules differed from that in the A-granules throughout development. © 1991, Academic Press Limited. All rights reserved.