Relation between O3-Inhibition of photosynthesis and salicylic acid in paddy rice grown with different CO2 concentrations

Abstract

This study was conducted to evaluate the role of salicylic acid (SA) on 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 given different atmospheric carbon dioxide concentrations (CO2: 400 and 800 cm3 m -3; C400 and C800, respectively). Salicylic acid solutions (0, 0.1, and 1 mM; S0, S0.1, and S 1, respectively) were applied as a pretreatment one day before O 3 exposure. 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) 5-h O3 exposure. The photosynthesis-related parameters, total ascorbic acid, and redox state of ascorbic acid (RDS) were decreased by O3 exposure. The O3-induced reduction of PN, ascorbic acid content, and its RDS were ameliorated by C800. Salicylic acid ameliorated the O3-inhibition of net photosynthetic rate (PN) slightly, and O3-induced depletion of total ascorbic acid and RDS substantially. SA did not increase PN in non-treated leaves (O0 plants). However, O3 exposure elevated the level of endogenous SA. These results show that SA plays a vital role in the defense response to acute O3 exposure in paddy rice. Effects of SA on O3-inhibition of PSII and ascorbic acid content were unaffected by elevated CO2 (C800).