ENDOGENOUS ETHYLENE AFFECTS THE BEHAVIOUR OF STOMATA IN EPIDERMIS ISOLATED FROM RUST INFECTED FABA BEAN (VICIA FABA L.).

Rust infection of proximal halves of leaves of Vicia faba L. potentiates the sustained production of ethylene by abiotically wounded but uninfected distal regions. When epidermal strips were isolated from distal regions, either before or after incubation in aqueous media, stomatal opening was inhibited compared to that in strips from leaves of healthy, control plants. This inhibition, and the even greater inhibition seen in strips from rusted tissues, was reversed to differing extents by inclusion in the medium of inhibitors of the action of ethylene, namely silver ions (6 × 10 mol m ), or of its biosynthesis, namely cobalt ions and AVG (both at 1 × 10 mol m ). When ACC, a precursor of ethylene, was supplied to healthy leaves it promoted ethylene evolution after wounding and inhibited stomatal opening in strips isolated from those leaves. The cytokinins zeatin and kinetin (1 × 10 mol m ) also promoted opening in strips from both healthy and rusted regions of infected leaves, but only fusicoccin (1 × 10 mol m ) promoted wide opening in rusted regions. It is proposed that endogenous ethylene is an effective regulator of stomatal behaviour in epidermal strips prepared from either healthy or rusted regions of infected leaves of V. faba.