Cereal Chem 65:404-408   |  VIEW ARTICLE

Localization and Physical Properties of Endogenous Germination Inhibitors in White Wheat Grain.

C. F. Morris and G. M. Paulsen. Copyright 1988 by the American Association of Cereal Chemists, Inc. 

Preharvest sprouting in wheat (Triticum aestivum L.) seriously reduces end-use quality of flour and is associated with lack of dormancy in mature seed. Knowledge of the location of endogenous germination inhibitor(s) within the wheat kernel and their solubility and chemical stability would greatly aid in the isolation, identification, and determination of the mode of action of these compound(s). Six mill fractions were produced from white wheat grain using laboratory break rolls and sieves. Fractions were break 2 large, medium, and small and break 3 bran, medium, and small. Break 2 large and break 3 bran and medium fractions were greatly enriched in bran, and the other three fractions were mostly endosperm. Endogenous germination inhibitory activity of water-soluble extracts of mill-fractions and whole-grain meal was measured by a wheat embryo bioassay. Inhibitory activity was mostly localized in the bran and little occurred in the endosperm fractions. Most inhibitory activity was soluble in water and up to 90% ethanol, insoluble in petroleum ether, and heat stable. The endogenous inhibitory activity was similar to 1 to 2.5 micromolar abscisic acid in its effect on germination of embryos from dormant wheat seeds. The results support the hypothesis that control of germination and preharvest sprouting resides in the embryo and is mediated by inhibitors in the bran.