Abstract
Tropospheric ozone (O3) is widely recognized as the cause of substantial yield and quality reduction in crops. Most of the previous studies focused on the exposure of wheat cultivars to elevated O3 levels. Our main objectives were to: (i) investigate the consistency of wheat cultivars’ physiological responses across two different realistic O3 levels; and (ii) compare these physiological responses with those under short acute O3 exposure. Three commercially available hard spring wheat cultivars bred under semiarid and Eastern Mediterranean conditions were exposed to two different O3 levels during two consecutive seasons (2016–2018)—36 and 71 ppbv 7 h mean O3 mixing ratios in open-top chambers. The results were compared to those following short acute O3 exposure (102.8 ppbv, 7 h mean for 10 days) in a greenhouse. Non-stomatal responses were significantly more pronounced than stomatal responses in all cultivars under different levels of O3. The specific cultivar was observed as the most O3-tolerant under all experiments. The fact that the same cultivar was found remarkably tolerant to the local semiarid ambient conditions according to other studies and to O3 exposure based on the present study supports a link between cultivar resistance to drought conditions and O3.
Highlights
Tropospheric ozone (O3) is a phytotoxic secondary air pollutant formed by complex photochemical reactions of ofrodrinpgartoamSteutedresnVt’scmt-atexsat.npd-VJabluyes ANofOfaVcAtoarsreOa3lseoxsphooswurne. (O3) precursors such as nitrogen oxides, carbon monoxide, methane, and volatile organic compounds [1]
The main objective of this study was to test the level of consistency of physiological response mechanisms to two realistic—slightly and moderately elevated—O3 levels
Our study indicates detrimental effects on physiological activities of all cultivars at all O3 enrichment levels, including the slightly elevated O3 exposure in the open-top chambers (OTCs) in season I (AOT40 = 0.902 ppmh; M7 = 36 ppbv), the cultivar-wise variations for season I were statistically less significant than those for season II
Summary
Tropospheric ozone (O3) is a phytotoxic secondary air pollutant formed by complex photochemical reactions of O3 precursors such as nitrogen oxides, carbon monoxide, methane, and volatile organic compounds [1]. O3 causes damage in plants following its penetration into leaves through the stomata; this leads to oxidative stress, initiating metabolically affluent defense mechanisms and accelerating senescence and reduction in photosynthesis, growth, biomass, and yield [5,6]. Both chronic and acute O3 exposure are known to affect photosynthesis, induce variation in stomatal responses, decrease in carboxylation efficiency of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), and reduce biomass and yield [2]. Exposure to O3 can damage leaves depending on the level and the duration, manifested as foliar injury symptoms on natural vegetation and crop plants [7]. Under elevated levels of O3, different crop plants showed visible foliar injury symptoms [9,10]
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