Radish ( Raphanus sativus L.) Cultivar‐Specific Response to O 3 : Patterns of Biochemical and Plant Growth Characteristics

The sensitivity of four radish ( Raphanus sativus L.) cultivars, Baladey “B,” Cherry Belle “CB,” Prinz Rotin “PR,” and Scarlet Globe “SG” to 80 nL L −1 ozone is assessed in fumigation chambers. O 3 visible injury symptoms appears as brown spots to chlorotic areas, but the response is cultivar‐specific. O 3 induces higher content of H 2 O 2 and lipid peroxidation (it is estimated as malondialdehyde (MDA) content), leading to drastic visible injury symptoms in B compared to the other cultivars. Root and shoot dry weights, Chlorophyll a , net photosynthetic rates, and chlorophyll fluorescence are reduced in B to a greater extent than the other cultivars. On the other hand, stomatal conductance increased in B and CB (+52 and +24%, respectively) due to O 3 ‐exposure, while it was decreased by 35% in PR and SG. Exposure to O 3 generates oxidative stress leading to stimulation of antioxidative defense systems. SG shows the highest induction of catalase (CAT), superoxide dismutase (SOD), and glutathione reductase (GR), while B had the lowest activities of these antioxidative enzymes, but had the highest H 2 O 2 and MDA content. The higher accumulation of H 2 O 2 , poor induction of antioxidative enzymes, and increased stomatal conductance led to severe visible injury and drastic inhibition in photosynthetic rates and growth in B than other cultivars depicting its higher sensitivity toward O 3 . Therefore, it can be used as a bioindicator for O 3 pollution worldwide.