Paper Reviewed

Zinta, G., Abdelgawad, H., Domagalska, M.A., Vergauwen, L., Knapen, D., Nijs, I., Janssens, I.A., Beemster, T.S. and Asard, H. 2014. Physiological, biochemical, and genome-wide transcriptional analysis reveals that elevated CO 2 mitigates the impact of combined heat wave and drought stress in Arabidopsis thaliana at multiple organizational levels. Global Change Biology 20: 3670-3685.

Noting that "climate extremes are often accompanied by extremes in other climate factors," such as when "heat waves typically occur together with periods of drought," Zinta et al. (2014) write that the combination of heat and water deficit "is known to have distinct and significantly greater effects on plants and ecosystems, than each applied separately," citing the work of Rizhsky et al. (2002), Wang and Huang (2004), Mittler (2006), De Boeck et al. (2011), Dreesen et al. (2012) and Bauweraerts et al. (2013). And, therefore, they grew Arabidopsis thaliana plants in large walk-in controlled-climate chambers maintained at atmospheric CO 2 concentrations of either 380 ppm (ambient) or 730 ppm (elevated), during which time the chambers were maintained at either normal climatic conditions or at combined heat wave and drought conditions, while the plants were periodically analyzed "at the level of growth, genome-wide transcriptional changes, photosynthesis and redox metabolism."

As a result of these efforts, Zinta et al. discovered that the elevated CO 2 treatment significantly mitigated the negative impacts of the combined heat and drought conditions that were apparent in plant biomass reduction (see figure below), photosynthesis inhibition, chlorophyll fluorescence decline, H 2 O 2 production, and protein oxidation. And their analyses of enzymatic and molecular antioxidants revealed that "the stress-mitigating CO 2 effect operates through up-regulation of antioxidant defense metabolism, as well as by reduced photorespiration resulting in lowered oxidative pressure."

In light of these several findings, the nine scientists from Belgium thus concluded that although exposure to future extreme climate episodes could negatively impact plant growth and production, "elevated CO 2 is likely to mitigate this effect."



Growth response of thale cress to combined heat and drought stress at ambient (380 ppm) and elevated CO 2 (730 ppm) concentrations. Growth response of thale cress to combined heat and drought stress at ambient (380 ppm) and elevated CO(730 ppm) concentrations.

References

Bauweraerts, I., Wertin, T.M., Ameye, M., McGuire, M.A., Teskey, R.O. and Steppe, K. 2013. The effect of heat waves, elevated CO 2 and low soil water availability on northern red oak (Quercus rubra L.) seedlings. Global Change Biology 19: 517-528.

DeBoeck, H.J., Dreesen, F.E., Janssens, I.A. and Nijs, I. 2011. Whole-system responses of experimental plant communities to climate extremes imposed in different seasons. New Phytologist 189: 806-817.

Dreesen, F.E., De Boeck, H.J., Janssens, I.A. and Nijs, I. 2012. Summer heat and drought extremes trigger unexpected changes in productivity of a temperate annual/biannual plant community. Environmental and Experimental Botany 79: 21-30.

Mittler, R. 2006. Abiotic stress, the field environment and stress combination. Trends in Plant Science 11: 15-19.

Rizhsky, L., Liang, H.J. and Mittler, R. 2002. The combined effect of drought stress and heat shock on gene expression in tobacco. Plant Physiology 130: 1143-1151.

Wang, Z.L. and Huang, B.R. 2004. Physiological recovery of Kentucky bluegrass from simultaneous drought and heat stress. Crop Science 44: 1729-1736.