SUGAR ACCUMULATION IN BARLEY AND RICE GROWN IN SOLUTIONS WITH LOW CONCENTRATIONS OF OXYGEN

Barley and rice, at the early tillering stage, were grown in aerated nutrient solutions (> 7 mg O2 l-1) and transferred to solutions of low O2 concentrations (< 0.5 mg l -1).For barley, low O2 concentrations during the first 5 days severely inhibited growth of seminal roots had less effect on nodal roots, and did not reduce shoot growth. Longer exposure to low O2 concentrations reduced shoot as well as root growth. Sugar concentrations in roots and shoots increased within 7 h after transfer of plants to low O2 concentrations. After 5 days at low O2 concentrations sugar concentrations were very high in fast growing nodal roots and in shoots, as well as in the slower growing seminal roots.In rice, low O2 concentrations increased sugar levels of roots during summer, but not during winter. In summer, the higher sugar levels at low O2 concentrations persisted throughout a diurnal cycle. In root apices, sugar concentrations were increased by low O2 concentrations, even though the experiment was done in winter and the bulk of the root system showed no difference in sugar levels.The data indicate that sugar accumulation, at low O2 concentrations, is caused by reduced growth and also that even apices of roots grown at low O2 concentrations have sufficient substrates for respiration. © 1979, Annals of Botany Company.