Paper Reviewed
Szoboszlay, M., Näther, A., Mitterbauer, E., Bender, J., Weigel, H.-J. and Tebbe, C.C. 2017. Response of the rhizosphere prokaryotic community of barley (Hordeum vulgare L.) to elevated atmospheric CO2 concentration in open-top chambers. MicrobiologyOpen 6: e462, doi:10.1002/mbo3.462.

In their recent work, Szoboszlay et al. (2017) investigated the impact of elevated CO2 on the diversity and composition of the bacterial community inhabiting the rhizosphere of winter barley (Hordeum vulgare, cv. Kathleen). Plants were grown in the field in open-top chambers under either ambient (400 ppm) or elevated (700 ppm during daylight hours only) CO2 concentrations at an agricultural field in Braunschweig, Germany. Several plant yield parameters were examined at harvest; while the soil bacterial composition was analyzed using Illumina MiSeq sequencing of 16s rRNA gene amplicons from rhizoplane and soil particles most closely attached to the plant root surfaces.

With respect to the impact of CO2 on barley yield parameters, the authors observed that elevated CO2 concentrations increased ear length, ear dry weight, grain weight (yield) and grain number by 18, 22, 24 and 20 percent, respectively. With respect to rhizosphere differences, Szoboszlay et al. report that (1) the "composition of the prokaryotic communities was very similar for both [CO2] treatments and (2) "there was no significant difference in community structure between the samples from the two treatments," albeit elevated CO2 resulted in "lower prokaryotic diversity in the rhizosphere."

Commenting on the lower prokaryotic diversity, Szoboszlay et al. say that it is likely due to increased rhizodeposition under elevated CO2, where elevated CO2 stimulates increased "nutrient input into the rhizosphere that selects for microorganisms that can efficiently grow on these plant-derived compounds." Thus, it would appear that both plant and soil microorganisms can benefit from atmospheric CO2 enrichment.