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CO2 Effects on a Parasite-Host Association
Reference
Hwangbo, J.-K., Seel, W.E. and Woodin, S.J.  2003.  Short-term exposure to elevated atmospheric CO2 benefits the growth of a facultative annual root hemiparasite, Rhinanthus minor (L.), more than that of its host, Poa pratensis (L.).  Journal of Experimental Botany 54: 1951-1955.

What was done
The authors grew Kentucky Bluegrass (Poa pratensis L.) with and without infection by the C3 chlorophyllous parasitic angiosperm Rhinanthus minor L. for eight weeks in open-top chambers maintained at ambient and elevated (650 ppm) CO2 concentrations.

What was learned
At the end of the study period, the parasite's biomass (when growing on its host) was significantly greater in the CO2-enriched chambers (+47%).  The Kentucky Bluegrass host, on the other hand, exhibited only a 10% increase in biomass in the absence of the parasite but, surprisingly, a 19% increase when infected by the parasite, although neither increase was significant.  Meanwhile, the combination of total host plus parasite biomass was significantly greater in the CO2-enriched chambers (+25%).

What it means
Although the increase in atmospheric CO2 concentration significantly increased the biomass of this facultative hemiparasite, which is found in natural and semi-natural grasslands throughout the UK and Europe, this stimulation of the parasite's growth did not adversely impact the productivity of its host.  In fact, there is a possibility it may have actually helped its host grow better.


Reviewed 17 March 2004