Oxygen Dependence of Elongation Growth and Oxygen Uptake in Maize Coleoptiles

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.

A Lab‐Built Respirometer for Plant and Animal Cell Culture

“…Oxygen Affinity Study. The OUR dependence on DO concentration has been described in mitochondria, cells, and tissues by a hyperbolic saturation‐type relation (James, 1953; Ding and Schopfer, 1995; Steinlechner‐Maran et al, 1996; Costa et al, 1997). Data used to generate this relationship can be obtained from two different experiments.…”

The Biophysical Basis of Cell Elongation and Organ Maturation in Coleoptiles of Rye Seedlings: Implications for Shoot Development1

“…The relationship between cell respiration and coleoptile elongation was analyzed by Ding and Schopfer (1995) with organ segments cut from maize seedlings. These authors measured a slight (5 ± 10%) auxin-induced stimulation in the rate of dark respiration.…”

“…For instance, the changes in total and irreversible length of auxinincubated coleoptile segments have been analysed and implications for the process of wall yielding discussed (Hohl and Schopfer, 1992;Hohl et al, 1995;Edelmann and Köhler, 1995). Turgor and osmotic pressure were determined in isolated, auxin-treated rye coleoptile segments up to 24 h after excision (Edelmann and Köhler, 1995) and the changes in metabolic activity of such organ segments were recorded (Ding and Schopfer, 1995). However, no such data are available for the intact coleoptile, which ceases to elongate and matures after the emergence of the primary leaf (Cosgrove and Li, 1993;Fröhlich and Kutschera, 1995;Cleland, 1986, Niklas, 1992.…”