Production of α-Amylase Isozymes in Barley Caryopses in the Absence of Embryos and Exogenous Gibberellic Acid

Abstract

The isozyme composition and kinetics of production of α-amylase were studied in three samples of barley. Acid-dehusked caryopses and endosperm halves from a sample of Klages and from two samples of Clipper that differed in their ability to produce α-amylase in the absence of added gibberellic acid were incubated on moist sand at two temperatures in the presence or absence of gibberellic acid. The isozyme composition of the extracts was analysed on isoelectric-focusing-polyacrylamide gels and chromatofocusing columns. The endosperm halves of Klages and Clipper (type A) produced very low levels of enzyme in the absence of gibberellic acid while similar amounts of enzyme activity were found in both (+) and (-) gibberellic acid-treated incubates of Clipper (type B) endosperm halves. In these latter incubates, the initial kinetics of production, the proportion of α-amylase 1 to total enzyme activity and the effect of incubation temperature on the kinetics of production in both acid-dehusked caryopses and endosperm halves were similar, and were comparable to those observed in gibberellic acid-treated incubates of Klages and Clipper (type A). Since Clipper (type B) endosperm halves can produce α-amylase in the absence of added gibberellic acid, its role in this process should be reexamined.