Flooding usually reduced shoot and root growth of barley. In addition, root growth was inhibited much more in flooding-sensitive than flooding-tolerant cultivars. Prolonged flooding resulted in larger increases in activity of alcohol dehydrogenase (ADH) in roots of flooding-tolerant than flooding-sensitive cultivars.
Barley and rice were also grown in solutions flushed with gases of different oxygen concentration. In rice roots, high activities of ADH and pyruvate decarboxylase (PDC) were found only when the solutions were flushed with pure N2 gas. In barley roots, activities of ADH and PDC were highest using gases between 3 and 13% O2, lower with pure N2, and very low when using 20% O2.
These results indicate that the level of ADH occurring in plant roots will be very dependent on experimental conditions, as for example root density. Species differences in activity of ADH might be mainly related to different oxygen tensions inside the roots, due in turn to differences in volume of aerenchyma and morphology of roots.