Relation between O3-inhibition of photosynthesis and ethylene in paddy rice grown under different CO2 concentrations

Abstract

This study was conducted to evaluate the role of ethylene in acute ozone (O3: 0, 0.1, and 0.3 cm3 m–3; O0, O0.1 and O0.3, respectively)-induced photosynthetic inhibition of paddy rice leaves grown under different atmospheric carbon dioxide concentrations (CO2: 400 and 800 cm3 m–3; C400and C800, respectively). Ethephon and silver thiosulfate complex (STS) were applied one day before exposure to O3. Gas exchange, chlorophyll fluorescence, and ascorbic acid were measured immediately before (BE), immediately after (AE-0), and 1 d and 3 d after (AE-1, AE-3) the start of the exposure to O3. In the plants exposed to O3, visible leaf symptoms on the adaxial leaf surface appeared at AE-3. O3 decreased photosynthesis-related parameters, total ascorbic acid content, and redox state of ascorbic acid (RDS), and C800 ameliorated O3-induced damage. STS ameliorated the O3-induced visible leaf symptoms and O3-inhibition of photosynthesis but ethephon worsened slightly or did not affect them. Additionally, we evaluated the effects of O3 and CO2 on ethylene production in rice leaves. Although elevated CO2 did not affect ethylene production, exposure to O3 greatly increased ethylene production at AE-0 and rapidly reduced it at AE-1. These results indicate that ethylene is an important component of signal transduction for the extension of O3injury in paddy rice.