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Elevated CO2 Ameliorates the Negative Impact of Ozone Damage in Wheat

Paper Reviewed
Abdelhaliem, E. and Al-Huqail, A.A. 2016. Detection of protein and DNA damage induced by elevated carbon dioxide and ozone in Triticum aestivum L. using biomarker and comet assay. Genetics and Molecular Research 15: DOI http://dx.doi.org/10.4238/gmr.15028736.

Writing as an introduction to their work, Abdelhaliem and Al-Huqail (2016) note that ozone (O3) is "considered to be the most phytotoxic regional scale air pollutant owing to its high oxidative capacity, which involves the induction of reactive oxygen species (ROS) in plant cells," the latter of which "are highly toxic and induce changes in proteins, and cause oxidative DNA lesions." And given that O3 and carbon dioxide (CO2) concentrations are both expected to increase in the future, the two researchers designed a study "to compare the genetic effects of elevated CO2 and O3, alone or in combination, under irrigated and non-irrigated conditions on proteins and DNA of wheat (Triticum aestivum L.)."

In carrying out their objective, Abdelhaliem and Al-Huqail grew wheat from grains to harvest in earthenware pots inside open-top chambers, subjecting the harvested seeds to a series of biochemical, molecular and comet analyses. Chamber treatments included two CO2 levels (ambient and 580 ppm), two O3 levels (ambient and 120 ppb) and two water levels (irrigated with moisture levels kept near field capacity and non-irrigated) that were administered alone or in combination. Elevated CO2 and O3 levels were maintained from 11.00 to 15.00 h.

In discussing their findings, Abdelhaliem and Al-Huqail report that "protein, isozymes, and DNA have variable responses to elevated CO2 and O3, alone and in combination under irrigated and non-irrigated systems." In this regard, they note that the wheat plants were found to be highly sensitive to O3 damage, especially in the non-irrigated regime. However, the two scientists say that "the most notable finding in [their] study was that elevated CO2 could ameliorate the negative impact of elevated O3 on proteins and DNA." This reduction in O3-induced oxidative damage, they add, "may be due to reduced stomatal conductance as a result of elevated CO2 suppressing the entry of O3 through stomata (Mishra et al., 2013) or by increasing the levels of antioxidant defense in wheat cells which result in reducing high levels of ROS induced by O3 (Xu et al., 2015)."

Whatever the case, the above findings represent good news for wheat growers, especially in regions where elevated O3 is indeed a pollutant problem. And that is yet another reason to celebrate CO2!

References
Mishra, A.K., Rai, R. and Agrawal, S.B. 2013. Individual and interactive effects of elevated carbon dioxide and ozone on tropical wheat (Triticum aestivum L.) cultivars with special emphasis on ROS generation and activation of antioxidant defense system. Indian Journal of Biochemistry and Biophysics 50: 139-149.

Xu, Z., Jiang, Y. and Zhou, G. 2015. Response and adaptation of photosynthesis, respiration, and antioxidant systems to elevated CO2 with environmental stress in plants. Frontiers in Plant Science 6: 1-17.

Posted 4 April 2017