Paper Reviewed
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 6:10.3389/fpls.2015.00701.

In an enlightening report, Xu et al. (2015) "present a synthesis focusing on the underlying mechanisms in the responses to elevated CO2 at multiple scales, including molecular, cellular, biochemical, physiological and individual aspects, particularly, for these biological processes under elevated CO2 with other key abiotic stresses, such as heat, drought, and ozone pollution, as well as nitrogen limitation." And what did this huge undertaking reveal?

In the words of the three Chinese researchers, "most of the relevant studies have concluded that CO2 fertilization may mitigate the adverse impacts of environmental stresses, such as heat, drought, O3 pollution and their combinations," citing Biswas et al. (2013), Xu et al. (2013, 2014) and Zinta et al. (2014). More specifically, they note that "these aspects of the mitigation of CO2 enrichment include [1] relatively increased individual growth (e.g., Xu et al., 2014) and [2] community production (Naudts et al., 2014), [3] enhanced photosynthesis (Biswas et al., 2013; Xu et al., 2014; Zinta et al. (2014), [4,5] elevated water use efficiency and nitrogen use efficiency (Palmroth et al. 2013), [6] optimized chlorophyll fluorescence (Biswas et al., 2013; Xu et al., 2014; Zinta et al., 2014), [7,8] up-regulated antioxidant defense metabolism via increased lipophilic antioxidants and membrane-protecting enzymes (Naudts et al., 2014; Xu et al., 2014), and [9] decreased photorespiration with low H2O2 production (Foyer and Noctor, 2009; Munne-Bosch et al., 2013; Zinta et al., 2014)."

In concluding, therefore, Xu et al. (2015) express their hope that their thorough review of the subject may help provide "a better understanding of how plants deal with elevated CO2 using other mainstream abiotic factors, including molecular, cellular, biochemical, physiological, and whole individual processes." And these facts suggest that the planet's plant life is well equipped to successfully deal with the ongoing increase in the atmosphere's CO2 concentration ... and maybe even benefit from it.

References
Biswas, D.K., Xu, H., Li, Y.G., Ma, B.L. and Jiang, G.M. 2013. Modification of photosynthesis and growth responses to elevated CO2 by ozone in two cultivars of winter wheat with different years of release. Journal of Experimental Botany 64: 1485-1496.

Foyer, C.H. and Noctor, G. 2009. Redox regulation in photosynthetic organisms: signaling, acclimation, and practical implications. Antioxidants and Redox Signaling 11: 861-905.

Munne-Bosch, S., Queval, G. and Foyer, C.H. 2013. The impact of global change factors on redox signaling underpinning stress tolerance. Plant Physiology 161: 5-19.

Naudts, K., Van Den Berge, J., Farfan, E., Rose, P., AbdElgawad, H., Ceulemans, R., Janssens, I.A., Asard, H. and Nijs, I. 2014. Future climate alleviates stress impact on grassland productivity through altered antioxidant capacity. Environmental and Experimental Botany 99: 150-158.

Palmroth, S., Katul, G.G., Maier, C.A., Ward, E., Manzoni, S. and Vico, G. 2013. On the complementary relationship between marginal nitrogen and water-use efficiencies among Pinus taeda leaves grown under ambient and CO2-enriched environments. Annals of Botany 111: 467-477.

Xu, Z.Z, Shimizu, H., Ito, S., Yagasaki, Y., Zou, C.J., Zhou, G.S. and Zheng, Y.R. 2014. Effects of elevated CO2, warming and precipitation change on plant growth, photosynthesis and peroxidation in dominant species from North China grassland. Planta 239: 421-435.

Xu, Z.Z., Shimizu, H., Yagasaki, Y., Ito, S., Zheng, Y.R. and Zhou, G.S. 2013. Interactive effects of elevated CO2, drought, and warming on plants. Journal of Plant Growth Regulation 32: 692-707.

Zinta, G., AbdElgawad, H., Domagalska, M.A., Vergauwen, L., Knapen, D., Nijs, I., Janssens, I.A., Beemster, G.T.S. and Asard, H. 2014. Physiological, biochemical, and genome-wide transcriptional analysis reveals that elevated CO2 mitigates the impact of combined heat wave and drought stress in Arabidopsis thaliana at multiple organizational levels. Global Change Biology 20: 3670-3685.