Keywords: 
• ozone /
• Tagetes erecta Linn. /
• Petunia hybrida Vilm /
• Pharbitis purpurea (L.) Voigt /
• plasmalemma lipid peroxidation /
• soluble protein /
• phytohormone responses

Abstract: Elevated tropospheric ozone (O₃) is detrimental to urban greening plants by degrading their aesthetic and social values. It is urgent to clarify the possible physiological mechanisms on different responses of plant species to O₃ injury. In the present study, with open-top chamber method, marigold (Tagetes erecta Linn.), petunia (Petunia hybrida Vilm.) and morning glory (Pharbitis purpurea (L.) Voigt) were exposed to different O₃ concentration treatments to investigate foliar injury and leaf plasmalemma, soluble protein and endogenous phytohormone responses to O₃. The results showed that: 1) elevated O₃ resulted in yellowing lesions between veins on the upper leaves surface of marigold and petunia, and white spotting on morning glory leaves. The lesions intensified with increasing O₃ concentration and exposure duration; 2) O₃ exposure exacerbated membrane lipid peroxidation, but did not significantly influence soluble protein content, indicating that O₃ did not weaken plant defense ability brought about by protein in later growth stage; 3) elevated O₃ significantly decreased jasmonic acid (JA) content of marigold and morning glory leaves, and enhanced salicylic acid content (SA) of petunia and morning glory leaves, indicating the distinct phytohormone responses to O₃ among species. O₃ injury was caused from weakened JA protection capability for marigold leaves, increased SA accumulation for petunia leaves, and both above changes for morning glory leaves. In order to maximize the ecological benefits, the different phytohormones response relating to O₃ injury should be identified and the specific protective measures could be adopted in face of rising tropospheric O₃ concentration.