No abstract

Auxin‐mediated elongation growth of maize coleoptile segments is inhibited by reducing the O2 concentration in the incubation medium to GT 100 μmol . 1−1. The half‐maximal elongation rate is reached at 40 μmol . 1−1 O2, i.e. about two orders of magnitude higher than with mitochondrial respiration. O2 uptake of the segments measured under similar conditions with an O2 electrode shows a very similar dependence on O2 concentration. Auxin increases O2 uptake by 5–10% when it induces growth. About 40% of the O2 uptake is insensitive to inhibition by KCN. Auxin has no effect on O2 uptake in the presence of KCN. The possibility that auxin‐mediated elongation growth depends on a KCN‐sensitive oxidative process, other than cytochrome c oxidase‐catalyzed respiration, is discussed.