Anaerobic carbohydrate metabolism in wheat and barley, two anoxia-intolerant cereal seeds

Abstract

Cereals such as barley and wheat are unable to germinate under anoxic conditions. Data are presented on the utilization of the soluble sugars present in the dry seed of wheat and barley kept under strict anoxia, together with the status of the enzymes involved in the metabolism of carbohydrates. The amount of glucose, fructose, and sucrose decreases during the anaerobic treatment, indicating that carbohydrate metabolism takes place in the seeds of wheat and barley kept under anoxic conditions. The analysis of the enzymes involved in the metabolism of carbohydrates shows that the enzymatic set needed to convert sucrose, glucose, and fructose to glucose-6P is present in the anaerobic seeds. Sucrose degradation seemingly occurs through a sucrose synthase pathway with nucleoside diphosphate kinase involved in the cycling of urydilates. However, the activity of sucrose synthase, glucokinase, and fructokinase, all strongly induced in rice, an anoxia-tolerant cereal, are almost unaffected or even depressed in the two cereal seeds under investigation. The comparison of the results obtained and described in this paper with the published data on the metabolism of carbohydrates in rice, indicate that the anoxia-intolerant species would rapidly suffer and eventually die from sugar starvation if kept under anoxia for a relatively prolonged length of time (4-8 d).