Induction of Sensitivity to Gibberellic Acid in Developing Wheat Caryopses: Effect of Rate of Desiccation

Abstract

No change in the total β-amylase activity, attributable to the presence of 10^-6 M gibberellic acid (GA³) in the incubation medium, was found in freshly harvested, de-embryonated, immature (11-38 days post-anthesis) caryopses of wheat. Significant amounts of GA³-induced α-amylase activity was found in 26-h incubates of similar caryopses which had been allowed to dry out either in the ear or detached from the ear.

After 10 days of storage of detached immature caryopses in air of 99-100% relative humidity, de-embryonated half-caryopses responded to applied GA³ by producing α-amylase. More α-amylase was found in 26-h incubates if detached caryopses dried out slowly, but rapid desiccation led to little or no α-amylase being produced in the presence of GA³.

Caryopses taken from ears cultured on 0.4 or 4% sucrose for 10 days did not respond to applied GA³ whereas those from ears cultured on water did respond, although the amount produced in 26-h incubates was not as large as those from slowly dried ears.

Development of the ability to respond to GA³ by increasing α-amylase activity depended on the duration of desiccation or isolation from the plant. Changes in metabolism emanating from the interruption to the supply of sucrose to the caryopsis may be involved in the development of the ability of the aleurone to respond to GA³.