Slowdown of elongation growth and auxin-mediated growth response observed in ageing maize coleoptiles are caused by de-creasing elastic and plastic cell wall extensibility. Hydrogen peroxide quantity and peroxidases activity increase in the apoplast of ageing coleoptiles. Since cell wall elasticity in vitro decreases due to exogenous hydrogen peroxide in fresh cut coleoptiles, it is possible to assume that the reduction of cell wall extensibility is derived from the increasing of oxi-dative processes catalyzed by peroxidases. Reduction of cell wall extensibility is one of the causes of elongation growth velocity decreasing.