Influence of Temperature During Grain Growth and Ripening of Barley on the Subsequent Response to Exogenous Gibberellic Acid

When endosperm halves taken from batches of Himalaya barley grown in the United Kingdom and in various years in the U.S.A. and from Clipper barley grown in South Australia were incubated in either the presence or absence of gibberellic acid, variability in the production of α-amylase was found between batches. Samples from selected batches were grown in glasshouse conditions in winter and in summer. The amount of α-amylase produced in either the presence or absence of gibberellic acid depended on the environmental conditions operating during grain filling and on drying temperature of ears harvested late in grain filling. Two reponse-types of endosperm were distinguished: type A had a strict requirement for exogenous gibberellic acid, whereas type B did not. Himalaya ears grown at temperatures greater than 20°C in controlled environment conditions produced type B endosperm. Similar kinetics of production of °-amylase were found for both types. The notion that the high production of °-amylase in the absence of exogenous gibberellic acid by type B endosperm was induced by high amounts of endogenous gibberellin-like materials was not supported by experiments where either endosperm halves or stacks of endosperm slices of both types were incubated together.