Starch from Hull-less Barley: Ultrastructure and Distribution of Granule-Bound Proteins

Starch granules isolated from waxy, normal, and high-amylose hull-less barley grains were examined by transmission electron microscopy with cytochemical techniques. The micrographs showed two distinct regions of different sizes: 1) densely packed granule growth rings (which varied in size and number depending on the genotype), and 2) a loose filamentous network located in the central region of the granule. The granule ring width decreased with increasing amylose content. In all three genotypes, the growth rings closer to the granule surface were narrower in width than those within the granule interior. The waxy starch had wider intercrystalline amorphous growth rings, semicrystalline growth rings, and more open crystalline lamellae than normal and high-amylose starches. Granule bound proteins (mainly integral proteins) were located in the central and peripheral (growth ring) regions of the granule.