Combined Acute Ozone and Water Stress Alters the Quantitative Relationships between O3 Uptake, Photosynthetic Characteristics and Volatile Emissions in Brassica nigra

Abstract

Ozone (O3) entry into plant leaves depends on atmospheric O3 concentration, exposure time and openness of stomata. O3 negatively impacts photosynthesis rate (A) and might induce the release of reactive volatile organic compounds (VOCs) that can quench O3, and thereby partly ameliorate O3 stress. Water stress reduces stomatal conductance (gs) and O3 uptake and can affect VOC release and O3 quenching by VOC, but the interactive effects of O3 exposure and water stress, as possibly mediated by VOC, are poorly understood. Well-watered (WW) and water-stressed (WS) Brassica nigra plants were exposed to 250 and 550 ppb O3 for 1 h, and O3 uptake rates, photosynthetic characteristics and VOC emissions were measured through 22 h recovery. The highest O3 uptake was observed in WW plants exposed to 550 ppb O3 with the greatest reduction and poorest recovery of gs and A, and elicitation of lipoxygenase (LOX) pathway volatiles 10 min–1.5 h after exposure indicating cellular damage. Ozone uptake was similar in 250 ppb WW and 550 ppb WS plants and, in both treatments, O3-dependent reduction in photosynthetic characteristics was moderate and fully reversible, and VOC emissions were little affected. Water stress alone did not affect the total amount and composition of VOC emissions. The results indicate that drought ameliorated O3 stress by reducing O3 uptake through stomatal closure and the two stresses operated in an antagonistic manner in B. nigra.

Ozone stress response of leaf BVOC emission and photosynthesis in mountain birch (Betula pubescens spp. czerepanovii) depends on leaf age

“…The high metabolic costs are evident from plant stress from elevated chronic tropospheric O 3 , resulting in degrading crop yields and decreased forest growth from losses in photosynthetic carbon assimilation (Loreto & Schnitzler, 2010 ; Mills et al., 2011 ). This aligns with responses seen in BVOC emissions to abiotic stress from O 3 exposure, where, depending on the plant species and its O 3 tolerance, emissions were both induced or reduced (Esposito et al., 2016 ; Kask et al., 2021 ; Peron et al., 2021 ; Vitale et al., 2008 ). Exposure to O 3 for extended periods also led to changes in the BVOC blend, mainly with induced MT emissions (Loreto et al., 2004 ; Moura et al., 2022 ; Rinnan et al., 2005 ).…”