Effects of Elevated Temperature and Ozone in Brassica juncea L.: Growth, Physiology, and ROS Accumulation

Abstract

Global warming and ozone (O3) 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−1) and elevated O3 concentrations (100 ± 10 nL L−1) on the growth, physiology, and reactive oxygen species (ROS) accumulation of leaf mustard (Brassica juncea L.). The aim was to examine whether elevated temperature increase the O3 damage due to increasing stomatal conductance, and thus, O3 flux into the leaf. Significant reductions in photosynthetic rates occurred under O (elevated O3 with optimal temperatures) and OT (elevated O3 and temperature) conditions compared to C (controls). Stomatal conductance was significantly higher under T than in the C at 7 DAE. Under OT conditions, O3 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 O3 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 O3 damage to B. juncea by increasing stomatal conductance and O3 flux into leaves.

Regulation of ROS Metabolism in Plants under Environmental Stress: A Review of Recent Experimental Evidence

“…In wheat, exposure to O 3 showed an increase in H 2 O 2 , O 2 •− , OH • and MDA levels [ 138 ]. Lee et al [ 139 ] reported an increase in MDA under O 3 (86 and 56%) stress compared to controls at 7 and 14 days after exposure, respectively. A similar trend was shown for O 3 exposure regarding H 2 O 2 , O 2 •− , and • OH [ 139 ].…”

“…Lee et al [ 139 ] reported an increase in MDA under O 3 (86 and 56%) stress compared to controls at 7 and 14 days after exposure, respectively. A similar trend was shown for O 3 exposure regarding H 2 O 2 , O 2 •− , and • OH [ 139 ]. Ozone-induced oxidative stress is also associated with the alteration in gas exchange, photosynthetic efficiency, and water relations [ 140 , 141 , 142 ].…”

Evaluation of the Importance of Some East Asian Tree Species for Refinement of Air Quality by Estimating Air Pollution Tolerance Index, Anticipated Performance Index, and Air Pollutant Uptake

“…Leaf gas exchange was measured according to a previously reported method [36] using the LI-6400XT Portable Photosynthesis system (LI-6400XT; Li-Cor Inc., Lincoln, NE, USA) equipped with a leaf cuvette that enables artificial LED Red and Blue light sources (6400-02B; LI-COR Inc., NE, Lincoln, USA). During measurements, conditions inside the LI-6400XT cuvettes were set up to match as follows: The cuvette block temperature was fixed at 25 • C, CO 2 concentration was 400 µmol mol −1 , photosynthetic photon flux density (PPFD) was 1000 µmol m −2 s −1 , and the relative humidity was 50-55%.…”

“…O 3 uptake through leaf stomata was calculated by dividing leaf conductance by the ratio of the binary diffusivities for water vapor and O 3 in air (1.68) and multiplying by the O 3 concentration in the chamber at the time of measuring water vapor conductance [36]. The O 3 uptake rate, Q, was calculated using the following Equation (2) [37].…”

Morpho-Physio-Biochemical Attributes of Roadside Trees as Potential Tools for Biomonitoring of Air Quality and Environmental Health in Urban Areas

“…However, under field conditions, long-term exposure to air pollution triggers a decline in urban trees and forests. First, air pollution inhibits photosynthesis, resulting in a decrease in plant growth [8,9]. According to White et al (1974) [10], diverse pollutant mixtures have synergistic effects on tree photosynthesis.…”