Response of Barley Shoot Apices to Application of Gibberellic Acid: Initial Response Pattern.

Abstract

Seedlings of barley (Hordeum vulgare L. cv. Clipper) were grown in either controlled-environment chambers or in a frost-free glasshouse in short days and were treated with aqueous gibberellic acid solutions at the 1½-leaf stage.

A single application of gibberellic acid resulted in enhanced rates of growth of the apex and subjacent leaf primordia for only a relatively short period in the life cycle of the plant. The first morphological response to the treatment was an increased dome length, which was followed by increased rates of growth and development of subjacent leaf primordia and basal spikelet primordia. After the period of enhancement, the growth rates of the apices of the treated plants fell to values comparable to those of the control plants.