Induction of Sensitivity to Gibberellic Acid in Developing Wheat Caryopses: Effect of Sugars in the Culture Medium

Abstract

The influence of sugars in culture media on the development of the ability of the aleurone layer to respond to gibberellic acid was investigated by culturing detached wheat ears for 6 days and then measuring the hormone-induced α-amylase activity in incubates of endosperm halves derived from the cultured ears. Some response to gibberellic acid was found after ears had been cultured on water, or on solutions of either sorbitol or mannitol. Addition of mineral nutrients plus glutamine to these culture media reduced the response. Likewise, the addition of sucrose, glucose and/or fructose or galactose reduced the response, and a complete culture medium abolished the response, giving endosperm halves which were similar to those from ears retained on the plant.

Supplying mannose to the culture medium yielded endosperm halves as responsive to gibberellic acid as those from fully air-dried caryopses. The separate effects of mannose and sucrose were concentration dependent in the range 1-10 mM. Adding mannose and/or glucose to GA₃-containing incubates of endosperm halves did not alter the intensity of α-amylase activity in these incubates. The results were interpreted as an effect of the sugars on the metabolic status of the inflorescence.