Involvement of superoxide generation in salicylic acid-induced stomatal closure in Vicia faba

Abstract

Salicylic acid (SA), the known mediator of systemic acquired resistance, induced stomatal closure of Vicia faba L. Application of SA to the epidermal peels evoked an elevation of chemiluminescence of Cripridina lucigenin-derived chemiluminescent reagent (CLA) which is sensitive to superoxide anion (O2·-). The SA-induced generation of chemiluminescence was suppressed by O2·-specific scavengers superoxide dismutase (SOD) and 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron). These results suggest that O2·- was generated in epidermal peels by SA-treatment. A peroxidase inhibitor salicylhydroxamic acid (SHAM) inhibited guaiacol peroxidase activity and suppressed the SA-induced CLA chemiluminescence in the epidermal peels, suggesting that O2·- generation occurred by the peroxidasecatalyzed reaction as proposed for SA-treated tobacco cell suspension culture [Kawano et al. (1998) Plant Cell Physiol. 39: 721]. SOD, Tiron or SHAM suppressed the SA-induced stomatal closure. Moreover, application of superoxidegenerating system also induced stomatal closure. These results support the concept of involvement of reactive oxygen species in signal transduction in SA-induced stomatal closure.