Stress‐relaxation Properties of the Avena Coleoptile Cell Wall

Changes in the cell wall properties of Avena coleoptile segments were studied under various conditions by stress‐relaxation analysis. Rheological models consisting of four or an infinite number of Maxwell viscoelastic components were used. The stress‐relaxation parameters of these models, t 1 , t o , T, Gi and stress/strain ratio, were determined. The following results were obtained. 1. The 1/T 1 increased and stress/strain ratio decreased with the age of the coleoptiles. Decapitation caused a decrease in l/t 1 . 2. Auxin increased I/T 1 but decreased t o and stress/strain ratio within 5 minutes after application. 3. Treatment with a fungal β‐l,3‐glucanase increased 1/T 1 both in living and methanol‐killed, pronase‐treated coleoptiles. Cellulase did not cause the changes observed in the parameters of the isolated cell wall of the coleoptile segments. This held true for all treatments (with and without auxin, killed and pronase‐treated). The results obtained suggest that auxin primarily causes a partial degradation of the non‐cellulosic physaccharide components of the cell wall.