Ameliorating effects of three kinds of antioxidants to ozone-polluted painted nettle (Coleus blumei Benth.)

Ground concentration of ozone (O-3) causes serious threat to plants. In order to protect sensitive plants from O-3 pollution, many kinds of antioxidants were assessed in previous studies. In this study, effects of O-3 fumigation (a single spike of 120 +/- 20 nmol mol(-1) for four hours) on an ornamental species (Coleus blumei) was examined in open-top chambers. Before the O-3 treatment, plants were sprayed respectively either with a solution of three different antioxidants [Na-ascorbate (NaAsA), kinetin (KIN), and spermidine (Spd)] or with distilled water to compare their protective effects to plants. Our results revealed that O-3 fumigation impaired the plasma membrane, decreased chlorophyll (Chl) content, inhibited photosynthesis, induced photoinhibition and photodamage, and caused visible injury. Spraying with KIN, NaAsA or Spd ameliorated the decrease of the Chl content and photosynthetic capability, the impairment of membrane, and visible injury under O-3 fumigation. The plants treated with KIN showed the best ability to mitigate the injury caused by O-3.