Effects of Reduced Supply of Oxygen on the Metabolism of Roots of Glyceria maxima and Pisum sativum

This work was done to see whether the general metabolism of roots of flood-tolerant Glyceria maxima showed any marked adaptation to lack of oxygen that distinguished them from roots of flood-intolerant Pisum sativum. We determined the effects of 14, 11, 8, 6, 4, 2 and 1% oxygen, and anoxia, on the metabolism of [U-¹⁴C]sucrose, and of that of ¹⁴CO₂ in the dark, by excised roots. No significant differences were found between the two species. The proportion of the metabolized label that was incorporated into polymers began to fall at 6% oxygen to reach in anoxia values that were only 10–30% of those in air. Glyceria roots formed aerenchyma. Glyceria plants, with shoots in air and roots in [U-¹⁴C]sucrose that lacked oxygen, readily incorporated ¹⁴C into polymers. This incorporation was greatly reduced when the shoots were cut off and the end of the stem sealed. We concluded that Glyceria roots show no major metabolic adaptation to hypoxia, and that their flood-tolerance is due mainly to aerenchyma. We related these conclusions to the metabolic theory of flood-tolerance.