Stimulation of Avena coleoptile growth by reduction of oxygen supply

The growth of Avena sativa L. coleoptiles was accelerated by reduction of the O2 concentration in the surrounding atmosphere. Cell-wall extensibility was increased in close relation to the increase in elongation, 6-8% O2 giving the optimal effect in either case. Growth promotion by reduced O2 concentration and by auxin (indole-3-acetic acid; IAA) were additive, at least at lower auxin concentrations.This response to reduced O2 concentration was also present in sections pretreated with cycloheximide for 2 h, although such sections showed no response to applied IAA. No significant change was observed in auxin transport under reduced O2 supply. It is suggested that the acceleration of cell elongation and the loosening of cell wall by reduced O2 supply are due to a mechanism which is not directly dependent on auxin-induced growth. We propose to designate this acceleration of growth under reduced O2 concentrations as oxygen-sensitive growth.