Development of Small Starch Granule in Barley Endosperm

The structural characteristics and physicochemical properties of barley starch differ with granule size, which are important in final product applications of barley flours. A barley (Hordeum vulgare L.) cultivar, Yangsimai 3, was used to investigate the development of small starch granule in endosperm under electron microscope to provide references to barley breeding. Large starch granules were formed and developed at the early stage of endosperm development. Large amyloplasts with large starch granules were divided and increased in number through binary fission. One large amyloplast had only 1 large starch granule. Small starch granules could be formed and develop at the middle and late stage of endosperm development. Endosperm cells had large amyloplasts that exhibited protrusion, and some of the protrusions contained small starch granules. Small amyloplasts with small starch granules formed new small amyloplasts to produce small starch granules by the way of protruding their envelopes. Many small starch granules were formed and developed in 1 small amyloplast. The amyloplast envelope began to degrade and release starch granules into cell matrix when amyloplast was full of starch granules. These results showed that small amyloplasts came from the protrusion of amyloplast envelopes. Many small starch granules, which were compound starch granules, were formed and developed in 1 small amyloplast.