The metabolism of carbohydrates is of importance for plant adaptation to anaerobic conditions. In this paper we show that rice seedlings synthesize sucrose under anoxic conditions. By contrast, barley is unable to synthesize sucrose under anaerobiosis. The activity of sucrose-phosphate synthase (EC 2.4.1.14 UDP-glucose: D-fructose-6-phosphate-2-glucosyl transferase), the most important enzyme for the synthesis of sucrose in plants, is not negatively affected by anaerobiosis in rice, while a negative effect on the activity of this enzyme is observed in anoxic barley grains.