Junli Wang Qing Zeng Jianguo Zhu Gang Liu Haoye Tang. Dissimilarity of ascorbate–glutathione (AsA–GSH) cycle mechanism in two rice (Oryza sativaL.) cultivars under experimental free-air ozone exposure.Agriculture Ecosystems & Environment 2013165: 39–49

Abstract

Rising tropospheric ozone concentrations ([O₃]) can lead to considerable damage to agricultural crops. Experimental data have shown that the relationship between O₃ injury and yield loss differs with crop species and that O₃ sensitivity differs among cultivars of the same species. To explore a breeding strategy to adapt crops to high [O₃] it is necessary to investigate the different mechanisms for cultivar resistance to O₃ stress. Although several chamber-based studies have examined antioxidant defence differences in rice (Oryza sativa L.) cultivars in response to elevated [O₃] such as the utilisation of the ascorbate–glutathione (AsA–GSH) cycle to eliminate reactive oxygen species (ROS) little research has been conducted under free-air O₃ enrichment (O₃-FACE) to address the different AsA–GSH cycle responses of rice cultivars. In this experiment O₃-FACE was used to investigate the AsA–GSH cycle in two rice cultivars SY63 (O₃-sensitive) and WXJ14 (O₃-resistant). The results indicated that compared with the ambient [O₃] elevated [O₃] (1.5 × ambient [O₃]) induced increases in the superoxide anion (O₂⁻) production rate hydrogen peroxide (H₂O₂) content malondialdehyde (MDA) content and relative electrical conductivity; increases that were greater in SY63 than in WXJ14. Continuous O₃ stress also resulted in a less efficient metabolism of the AsA–GSH cycle in SY63 compared to WXJ14. The results indicated that in SY63 elevated [O₃] accelerated ROS metabolism rates and the antioxidant system could not prevent oxidative damage thus increasing membrane lipid peroxidation. In contrast in WXJ14 there was transient damage in response to elevated [O₃] early in the sampling period which triggered the ROS to stimulate the antioxidant system to avoid O₃