| Summary: | Global warming and ozone (O<sub>3</sub>) pose serious threats to crop yield and ecosystem health. Although neither of these factors will act individually in reality, most studies have focused on the responses of plants to air pollution or climate change. Interactive effects of these remain poorly studied. Therefore, this study was conducted to assess the effects of optimal (22/20 °C day/night) and elevated temperature (27/25 °C) and/or ambient (10 ± 10 nL L<sup>−1</sup>) and elevated O<sub>3</sub> concentrations (100 ± 10 nL L<sup>−1</sup>) on the growth, physiology, and reactive oxygen species (ROS) accumulation of leaf mustard (<i>Brassica juncea</i> L.). The aim was to examine whether elevated temperature increase the O<sub>3</sub> damage due to increasing stomatal conductance, and thus, O<sub>3</sub> flux into the leaf. Significant reductions in photosynthetic rates occurred under O (elevated O<sub>3</sub> with optimal temperatures) and OT (elevated O<sub>3</sub> and temperature) conditions compared to C (controls). Stomatal conductance was significantly higher under T than in the C at 7 DAE. Under OT conditions, O<sub>3</sub> flux significantly increased compared to that in O conditions at 7 days after exposure (DAE). Significant reductions in total fresh and dry weight were observed under OT conditions compared to those under O. Furthermore, significant reductions in levels of carotenoids and ascorbic acid were observed under OT conditions compared to O. Lipid peroxidation and accumulation of ROS such as hydroxyl radical, hydrogen peroxide, and superoxide radical were higher under O and OT conditions than in C conditions at 7 and 14 DAE. As a result of O<sub>3</sub> stress, the results of the present study indicated that the plant injury index significantly increased under OT compared to O conditions. This result suggested that elevated temperature (+5 °C) may enhance O<sub>3</sub> damage to <i>B. juncea</i> by increasing stomatal conductance and O<sub>3</sub> flux into leaves.
|
|---|
