The Mechanisms by Which Tumbling and Abrasion Alter Enzyme Formation in Malting Grain

After applications of gibberellic acid tumbled, impacted and abraded grains formed α-amylase faster than untreated controls. Apparently apical abrasion was not essential to achieve this enhanced response. The testae of treated grains appeared to be intact, and excluded externally applied gibberellic acid except at the base of the grains, where it normally gains entry. Essentially normal patterns of modification were observed in all grain samples, however treated. Tumbling and abrasion sometimes stimulate enzyme production in the absence of externally supplied gibberellic acid. It is deduced that these treatments do not alter the pattern of gibberellin penetration into grain. Physical treatments cause limited embryo-damage and create fissures in and between the grain's surface layers. The treatments appear to exert their beneficial effects on enzyme production by allowing better access of oxygen in the air to the living grain tissues. Normally the oxygen supply limits enzyme formation. Surface populations of microbes sometimes limit oxygen levels in grain and repress enzyme formation.