Abstract
Ozone pollution is a damaging air pollutant that reduces maize yields equivalently to nutrient deficiency, heat, and aridity stress. Therefore, understanding the physiological and biochemical responses of maize to ozone pollution and identifying traits predictive of ozone tolerance is important. In this study, we examined the physiological, biochemical and yield responses of six maize hybrids to elevated ozone in the field using Free Air Ozone Enrichment. Elevated ozone stress reduced photosynthetic capacity, in vivo and in vitro, decreasing Rubisco content, but not activation state. Contrary to our hypotheses, variation in maize hybrid responses to ozone was not associated with stomatal limitation or antioxidant pools in maize. Rather, tolerance to ozone stress in the hybrid B73 × Mo17 was correlated with maintenance of leaf N content. Sensitive lines showed greater ozone‐induced senescence and loss of photosynthetic capacity compared to the tolerant line.
Highlights
The total Rubisco content, we report in this study, is similar to Rubisco content in maize reported by Salesse-Smith et al (2018), and we found that Rubisco content and activity decreased with leaf age, as previously reported (Sharwood et al, 2016)
We found that Rubisco content measured in a mature leaf in July was correlated to yield in maize lines exposed to elevated O3 (Figure 6)
Ozone pollution is an important stressor on plants that reduces crop yields around the world
Summary
Maize F1 hybrids B73 × Hp301, B73 × Mo17, B73 × NC338, Mo17 × Hp301, Mo17 × NC338, and NC338 × Hp301 were planted on May 13, 2018 at the FACE facility near Champaign, IL (40020 N, 88140 W, https://soyface.illinois.edu/). To quantify the initial amount of active Rubisco catalytic sites, 100 μl of supernatant was aliquoted into a tube with 22 μM 14C-CPBP (2.96 × 104 DPM nmol−1, prepared as described by Kubien et al, 2011) and placed on ice for 30 min. To quantify total Rubisco content in the sample, 100 μl of supernatant was aliquoted into a tube containing activation buffer and was incubated at room temperature for 20 min. Paired leaf samples to those used to determine Rubisco content and activation state were extracted as described above, samples were activated in 1 ml cuvettes containing assay buffer (100 mM EPPS-NaOH, pH 8.0, 10 mM MgCl2, 0.2 mM NADH, 20 mM NaHCO3, 1 mM ATP, pH 7.0, 5 mM phosphocreatine, pH 7.0, and 4% [v/v] coupling enzymes) for 15 minutes, and reactions initiated with the addition of 0.4 mM RuBP. Least squares means were estimated and used to compare means in ambient and elevated O3 within a genotype using pairwise comparisons
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