Figure 4.

Cellular and tissue localization of ACC oxidase activation, H₂O₂ accumulation, and visible injury. Plants were exposed to 250 nL L⁻¹ ozone for 5 h, and terminal leaflets from leaf number 2 from ozone-treated plants were analyzed for GUS activity regulated by the LE-ACO1 promoter 1 h after the beginning of the exposure (A), H₂O₂ accumulation 7 h after the beginning of the exposure (B), and ozone symptom localization after 24 h (C). D, Transverse section through a leaflet showing LE-ACO1 expression indicated by GUS staining at 1 h.