Genotypic differences in leaf biochemical, physiological and growth responses to ozone in 20 winter wheat cultivars released over the past 60 years

Abstract

Ozone (O 3 ) concentrations in periurban areas in East Asia are sufficiently high to decrease crop yield. However, little is known about the genotypic differences in O 3 sensitivity in winter wheat in relation to year of cultivar release. This paper reports genotypic variations in O 3 sensitivity in 20 winter wheat cultivars released over the past 60 years in China highlighting O 3 -induced mechanisms. Wheat plants were exposed to elevated O 3 (82 ppb O 3 , 7 h day À1 ) or charcoal-filtered air (o5 ppb O 3 ) for 21 days in open top chambers. Responses to O 3 were assessed by the levels of antioxidative activities, protein alteration, membrane lipid peroxidation, gas exchange, leaf chlorophyll, dark respiration and growth. We found that O 3 significantly reduced foliar ascorbate (À14%) and soluble protein (À22%), but increased peroxidase activity (146%) and malondialdehyde (1 38%). Elevated O 3 depressed light saturated net photosynthetic rate (À24%), stomatal conductance (À8%) and total chlorophyll (À11%), while stimulated dark respiration (1 28%) and intercellular CO 2 concentration (1 39%). O 3 also reduced overall plant growth, but to a greater extent in root (À32%) than in shoot (À17%) biomass. There was significant genotypic variation in potential sensitivity to O 3 that did not correlate to observed O 3 tolerance. Sensitivity to O 3 in cultivars of winter wheat progressed with year of release and correlated with stomatal conductance and dark respiration in O 3 -exposed plants. O 3 -induced loss in photosynthetic rate was attributed primarily to impaired activity of mesophyll cells and loss of integrity of cellular membrane as evidenced by increased intercellular CO 2 concentration and lipid peroxidation. Our findings demonstrated that higher sensitivity to O 3 in the more recently released cultivars was induced by higher stomatal conductance, larger reduction in antioxidative capacity and lower levels of dark respiration leading to higher oxidative damage to proteins and integrity of cellular membranes.

Assessing the impacts of current and future concentrations of surface ozone on crop yield with meta-analysis

“…Numerous studies have shown that elevated [O 3 ] generally results in reduced photosynthesis and whole-plant growth, decreased stomatal conductance, altered antioxidant system, and accelerated senescence, although the extent of the effects varies by species or even cultivars (Ainsworth, 2008;Ashmore, 2005;Biswas et al, 2008;Clarke et al, 1990;Feng et al, 2006Feng et al, , 2008; Long and Naidu, 2002;Morgan et al, 2003Morgan et al, , 2006. Furthermore, elevated [O 3 ] can increase respiration rates and affect carbon allocation patterns, resulting in a decreased root: shoot ratio (Andersen, 2003;Biswas et al, 2008;Feng et al, 2006;Nouchi et al, 1995), or decreases in the leaf area ratio and specific leaf area (e.g.…”

“…Furthermore, elevated [O 3 ] can increase respiration rates and affect carbon allocation patterns, resulting in a decreased root: shoot ratio (Andersen, 2003;Biswas et al, 2008;Feng et al, 2006;Nouchi et al, 1995), or decreases in the leaf area ratio and specific leaf area (e.g. Morgan et al, 2003).…”

Differential effects of ozone on photosynthesis of winter wheat among cultivars depend on antioxidative enzymes rather than stomatal conductance

“…The sensitivity of plants to O 3 has been linked to O 3 flux controlled by stomata (Dizengremel et al, 2009;Fiscus et al, 2005) and antioxidant capacity determined by antioxidant pools and enzymes (Biswas et al, 2008;Feng et al, 2010;Inada et al, 2012;Li et al, 2016;Wang et al, 2014aWang et al, , 2014b. However, there was no significant interaction between cultivar and O 3 in g s across the four measurements (Table 1, a a a a a a Fig.…”

“…It has been reported that modern wheat cultivars are more sensitive to O 3 than old accessions due to higher g s and lower levels of antioxidant capacity (Pleijel et al, 2006), and that they are subjected to larger oxidative damages to proteins and cellular membranes (Biswas et al, 2008). In this study, five modern cultivars showed variable reduction of A sat at mid-grain filling stage with a wide range from 16% to78% when exposed to an elevation of average 8 h- [O 3 ] (9:00-17:00) from 44.4 ppb to 56.4 ppb , which suggests the presence of intraspecific variation in the response to elevated [O 3 ].…”

“…Therefore, O 3 -induced reduction in A sat would be largely attributed to non-stomatal factors, i.e. impaired physiological activity of mesophyll cells (Akhtar et al, 2010;Biswas et al, 2008;Farage and Long, 1999). Further evidence was the increased Ci ( Fig.…”