This study was conducted to evaluate the role of ethylene in acute ozone (O
3: 0, 0.1, and 0.3 cm
3 m
–3; O
0, O
0.1 and O
0.3, respectively)-induced photosynthetic inhibition of paddy rice leaves grown under different atmospheric carbon dioxide concentrations (CO
2: 400 and 800 cm
3 m
–3; C
400 and C
800, respectively). Ethephon and silver thiosulfate complex (STS) were applied one day before exposure to O
3. 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 O
3. In the plants exposed to O
3, visible leaf symptoms on the adaxial leaf surface appeared at AE-3. O
3 decreased photosynthesis-related parameters, total ascorbic acid content, and redox state of ascorbic acid (RDS), and C
800 ameliorated O
3-induced damage. STS ameliorated the O
3-induced visible leaf symptoms and O
3-inhibition of photosynthesis but ethephon worsened slightly or did not affect them. Additionally, we evaluated the effects of O
3 and CO
2 on ethylene production in rice leaves. Although elevated CO
2 did not affect ethylene production, exposure to O
3 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 O
3 injury in paddy rice.
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