Involvement of the Antioxidative System in Tomato Response to Fusaric Acid Treatment

Changes in O2- and H2O2 generation as well as superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase activities were examined in fusaric acid-treated tomato leaves. Fusaric acid application resulted in a lasting activation of O2- and H2O2 production. Within the first day after toxin application the H2O2 scavenging enzymes: catalase and ascorbate peroxidase showed a strong activity decrease followed by a gradual recovery to the control level after 2 and 3 days. By contrast fusaric acid markedly stimulated peroxidase activity measured with guaiacol as well as ferulic and coumaric acids, and syringaldazine. The maximum activity increase, coinciding with the highest H2O2 level, was about two-fold and 5.5-fold for phenolic acids and syringaldazine, respectively. The results obtained are discussed in the light of the data on the role of activated oxygen species and enzymes of their metabolism in plant defence.