Observations on the Germ Aleurone of Barley. Morphology and Histochemistry

The germ aleurone over the embryonic axis of barley was examined in strips of tissue peeled off harvest-ripe grains. The germ aleurone is only one cell thick but resembles 'normal' aleurone in being composed of living cells with dense, lipid-rich cytoplasm and thick walls containing phenolic material. In contrast to the cells of the 'normal' aleurone, germ aleurone cells contain very few phytin or protein deposits. When the germ aleurone is ruptured during germination, the walls at the torn edge become thickened with shiny golden-brown material, and 'sealed' to the testa. Two days after germination, lignin can be detected in the walls of a single row of germ aleurone cells adjoining the scutellum. The role of the germ aleurone in defence against microorganisms is discussed. It is suggested that the metabolic activities in the germ aleurone in imbibed grains compete with the embryo for oxygen, and thus may be one of the factors which determine whether a grain germinates or remains dormant.