Seed Dormancy in Avena fatua. III. The Effect of Mechanical Injury on the Growth and Development of the Root and Scutellum

Abstract

When dormant, imbibed caryopses of Avena fatua L. were induced to germinate by piercing a hole in the seed coat (pericarp plus aleurone layer), the rate of germination and the pattern of embryo development were both related to the site of injury. Piercing the dormant caryopsis 1 mm from the radicle end induced emergence of the radicle within 24-36 h and prior to any growth response of the scutellum. This germination behavior was similar to that of intact, nondormant (afterripened) caryopses, which served as controls. When dormant caryopses were pierced on the abaxial surface 5 mm from the proximal end and 1 mm distal to the tip of the scutellum, elongation of the scutellum was initiated after 48-72 h and was associated with papillae formation, xylem differentiation, and cell division in the distal region of the scutellum. These scutellar responses preceded elongation of the radicle by ca. 24 h. The restricted distribution of the response to piercing and the ability of this treatment to initiate the resump...