Dormancy of the barley grain is correlated with gibberellic acid responsiveness of the isolated aleurone layer

Abstract

The relationship between barley grain dormancy and gibberellic acid (GA3) responsiveness of aleurone layers has been investigated. Barley (Hordeum distichum L. cvs Triumph and Kristina) grains were matured under defined conditions in a phytotron. Grains of Triumph plants grown under long-day/warm conditions had lower dormancy levels than grains of plants grown under short-day/cool conditions. Aleurone layers isolated from grains of long-day Triumph plants secreted more α-amylase and had a higher responsiveness to GA3 as measured by α-amylase secretion. Storage of the grains increased both the percentage of germination and the responsiveness of the aleurone to GA3. Use of different sterilization methods to break dormancy confirmed the correlation between germination percentage and aleurone layer GA3 responsiveness. The response of embryoless Triumph grains to GA3 was lower than that of the isolated aleurone layers, suggesting a role of the starchy endosperm in regulating the GA3 response of the aleurone layer. Grains of the cultivar Kristina harvested from short day- and long day-grown plants lacked dormancy, and their isolated aleurone layers had a similar responsiveness to GA3 as measured by α-amylase secretion. The data indicate that the physiological state of the aleurone layers contributes to the percentage germination of the grains.