Cereal Chem 67:59-63   |  VIEW ARTICLE

Size-Distribution of Wheat Starch Granules During Endosperm Development.

D. B. Bechtel, I. Zayas, L. Kaleikau, and Y. Pomeranz. Copyright 1990 by the American Association of Cereal Chemists, Inc. 

Starch granule development in hard red winter wheat was followed by light and electron microscopy and quantitative image analysis. Proplastids in the cytoplasm of the coenocytic endosperm two days after flowering (DAF) differentiated into amyloplasts by 4 DAF. Quantitative image analysis showed that the starch granules initiated during the first 4 DAF increased in size to mean diameter of 5.6 micrometers by 7 DAF. These early synthesized granules (type A) continued to enlarge to their maximum diameter of 25-50 micrometers some as soon as 19 DAF. A second group of starch granules, the small type B granules, was initiated at 10 DAF, was pronounced by 12 DAF, and did not enlarge during 12-19 DAF. These small granules began to enlarge at 21 DAF but only grew to a mean diameter of about 9 micrometers by maturity (35 DAF). A third group (designated type C) of small granules was initiated at 21 DAF. At maturity three distinct size groups of starch granules were present: large type A granules with diameters greater than 15.9 micrometers, Type B granules with equivalent diameters between 5.3 and 15.9 micrometers, and small type C granules with equivalent diameters less than 5.3 micrometers. At maturity, the total number of starch granules comprised 45.7% type C granules, 49.5% type B, and 4.8% type A. The type C granules constituted 3.4%, Type B 45.0%, and type A granules 51.6% of the total mass at maturity.