Auxin and hydrogen ion actions on light-grown pea epicotyl segments III. Effect of auxin and hydrogen ions on stress-relaxation properties

The effect of auxin and hydrogen ions on the stress-relaxationproperty of the cell wall was studied using light-grown peaepicotyl segments. Auxin pretreatment caused a decrease in theminimum relaxation time (T_o) of the cell wall of stem segmentsand the epidermis at different pH values, when auxin had beengiven to stem segments. The in vivo effect of hydrogen ionson the cell wall was found to be the same as that of auxin.The stress supported by the frozen-thawed epidermis relaxedfaster at pH 4.5 than at pH 6.5, resulting in a shorter maximumrelaxation time (T_m) at pH 4.5. This effect of low pH was inhibitedby low temperature. The incipient pH range producing this effecton Tm was found to be 5.2–5.8. (Received July 22, 1974; )