ABSTRACT
Two physiological types of barley kernels have been identified. They differ in their requirement for gibberellic acid (GA3) to induce alpha-amylase synthesis in deembryonated kernels. Type A grains produce alpha-amylase only when germinated with an embryo or incubated in the presence of GA3. On the other hand alpha-amylase is produced in Type B grains in the absence of both an embryo and GA3.
Type B grains have been experimentally produced in a number of Australian barley cultivars and have been found in samples of Clipper from the 1983 South Australian crop. Inhibitors of gibberellin biosynthesis applied to Type B kernels in the absence of GA3 have no effect on the production of alpha-amylase, indicating that an adequate amount of gibberellin may be present in the dry kernel. Although Type B kernels have been produced experimentally, the factors causing this development have not been fully delineated.
It is adduced that factors other than those examined may be of significance in the field situation and their possible interaction with the biosynthetic pathway of gibberellins is discussed.
