ABSTRACT
Two physiological types of barley grains have been found which differ in their response to the required stimulus for the production of α-amylase by the aleurone layer. Type A grains, the normal, produce α-amylase after treatment with gibberellic acid, and Type B, the atypical, only require water. The latter is found when barley ears are grown under high-intensity sodium lamps. When grown under other light sources, Type B grains are found in ‘Clipper’ ears grown at >21°C and harvested at the end of grain filling, and in ‘Himalaya’ ears grown at >24°C and harvested from the end of grain filling. Otherwise the typical variant (Type A) is found. The non-requirement for applied gibberellic acid in Type B endospem halves did not appear to be due to high residual amounts of endogenous gibberellin-like substances.
This environmentally induced transformation of the aleurone layer may have significant consequences in the understanding and control of preharvest spoilage.
