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The Interaction Between Elevated CO2 and Drought on Sweet Potato

Paper Reviewed
Saminathan, T., Alvarado, A., Lopez, C., Shinde, S., Gajanayake, B., Abburi, V.L., Vajja, V.G., Jagadeeswaran, G., Reddy, K.R., Nimmakayala, P. and Reddy, U.K. 2019. Elevated carbon dioxide and drought modulate physiology and storage-root development in sweet potato by regulating microRNAs. Functional & Integrative Genomics 19: 171-190.

According to Saminathan et al. (2019), sweet potato (Ipomoea batatas) is the seventh most-produced food crop worldwide and is a source of starch, ethanol, animal feed and other industrial products. However, there is concern with regard to how this important crop species will respond to predicted changes in climate in the years and decades to come, particularly with the stress of drought. Thus, the team of eleven researchers designed and conducted an experiment to investigate the interactive effects of elevated CO2 and drought on the growth of sweet potatoes.

To accomplish their goal, they grew plants of the variety Beauregard (B14) in a sunlit Soil-Plant-Atmosphere-Research (SPAR) facility under controlled environment conditions at the Rodney Foil Plant Science Research Center of Mississippi State University, Mississippi, USA. Sweet potato slips were transplanted into the SPAR chambers and exposed to one of two atmospheric CO2 concentrations, control (380 ppm) or elevated (760 ppm). Initially, all plants were grown under 100% field capacity water conditions. Then, at 41 days after transplanting (DAT), Saminathan et al. subjected half of the plants in each CO2 treatment to drought (40% water field capacity) until the experiment ended at 97 DAT.

Not surprisingly, the results of the experiment revealed that drought had a substantial negative impact on photosynthesis, chlorophyll and biomass of the sweet potato plants. In contrast, elevated CO2 improved these and other growth-related parameters. In the combined elevated CO2 and drought treatment, however, the positive effects of elevated CO2 more than sufficiently offset the negative effects of drought (see Figure 1 below). In this regard, Saminathan et al. say that "the decrease in photosynthesis under drought stress was mitigated by elevated CO2" and that "the significant reduction in biomass when plants were grown under drought was completely reversed under elevated CO2." What is more, they report that such mitigated responses were also found when biomass was apportioned into leaf, stem and root sinks.

In light of the above findings, the authors conclude that "elevated CO2 ameliorated the adverse effects of drought stress" on sweet potato. And that is wonderful news for this key global food crop that serves a variety of economic and dietary purposes.

Figure 1. Photosynthesis (left panel) and total biomass (right panel) response of sweet potato grown under different combinations of atmospheric CO2 (380 or 760 ppm) and water field capacity (FC; 100% or 40%). The percentages shown above the light green and light blue bars represent the percent increase in that parameter at a given water field capacity due to a 380 ppm increase in atmospheric CO2. Source: Saminathan et al. (2019).

Posted 13 February 2019