INCREASED ENDOSPERM MODIFICATION OF ABRADED BARLEY GRAIN AFTER GIBBERELLIC ACID TREATMENT*

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Abstract
Physiological and structural observations on barley grains revealed that the pericarp is impermeable to exogenous gibberellic acid. The use of a mechanical hand-mill abraded the pericarp at the non-embryo (distal) end of the grain without damaging the embryo or the overlying husk. When grown in gibberellic acid, the α-amylase content of these abraded grains was significantly higher than that of the controls. Malts prepared from abraded grains were visually identical with control malts prepared with gibberellic acid, but they gave higher hot water extracts. Grain abrasion permitted exogenous gibberellic acid to reach a larger number of aleurone cells, thus increasing the extent of endosperm modification during growth.