THE PERMEABILITY OF THE SURFACE LAYERS OF CEREAL GRAINS, AND IMPLICATIONS FOR TESTS OF ABRASION IN BARLEY

Abstract

The husk of barley, and the pericarps of naked, husked and ‘stripped’ barleys, of wheat and rye are more or less permeable to aqueous solutions of salts, or Eosin. The pericarps of stripped barley grains conduct aqueous solutions so that, for example, they conduct solutions of Eosin, or [14C]-gibberellic acid from the apex to the base of the grain where it accumulates in the embryo region. On the other hand the husk and pericarp are not so readily permeated by aqueous Trypan Blue. The testa/nucellar cuticle, together with the pigment strand, limits the inward penetration of salts and dyes. Gibberellic acid, and apparently water also, traversed the testae of some, but not all, decorticated barley grains, as demonstrated by the consequent modification of the starchy endosperms. However in most instances gibberellic acid solution does not traverse the surface layers of stripped grains and induce modification in their endosperms.