The Influence of the Pericarp and Testa on the Direct Passage of Gibberellic Acid Into the Aleurone of Normal and Abraded Barleys

The influence of the pericarp and testa of barley on the uptake of exogeneously applied gibberellic acid (GA3) was investigated using a method of ‘distal-soaking’ which allowed the grain to be soaked in test solutions without the interference of embryo growth. Using autoradiographic and enzymic studies it was observed that whilst the testa of mature or immature barley was pervious to gibberellic acid the pericarp was not. Pericarp abrasion allowed the hormone to enter the distal areas of abraded grains, causing improved distribution of endosperm-degrading enzymes. Microscopic studies confirmed that endosperm breakdown progressed from both ends of abraded grains while in control grains modification proceeded distally and asymmetrically from the embryo.