How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Effects of Elevated CO2 on a Parasitic Plant and its Host
Dale, H. and Press, M.C.  1999.  Elevated atmospheric CO2 influences the interaction between the parasitic angiosperm Orobanche minor and its host Trifolium repensNew Phytologist 140: 65-73.

What was done
Orobanche minor is an important agricultural weed, particularly in the UK and in the Middle East where it infects primarily leguminous crops.  Because this parasitic plant obtains all its carbon, nutrients, and water from its host, host plants generally accumulate less biomass than uninfected plants.  In order to study the effects of elevated CO2 on parasite-host interactions, the authors grew Trifolium repens with and without infection by Orobanche minor for 75 days in growth cabinets receiving atmospheric CO2 concentrations of 360 and 550 ppm.

What was learned
After 75 days of differential CO2 exposure, there were no significant differences in the biomass of uninfected Trifolium repens plants.  As expected, however, at ambient CO2 concentration, infected plants contained 47% less biomass than uninfected control plants.  In contrast, atmospheric CO2 enrichment partially alleviated biomass reductions resulting from infection by Orobanche minor; for infected plants grown at 550 ppm CO2 exhibited final dry weights that were only 20% less than those displayed by their respective controls.

As far as the parasitic plant is concerned, atmospheric CO2 enrichment did not affect the total biomass of Orobanche minor per host.  Nor did elevated CO2 impact the number of parasites supported by each host plant, or the time to parasitic attachment to host roots.  Thus, there were no detectable positive effects of elevated CO2 on the growth and performance of the parasite.

What it means
As the air's CO2 content rises, it is likely that the parasitic plant Orobanche minor will not exhibit any stimulation in its growth and development.  However, it is likely that the rising CO2 content of the air will partially alleviate biomass reductions in host leguminous plants infected by this parasite.  Thus, in a future world with higher atmospheric CO2 concentrations, greater yields can be expected for leguminous crops that currently suffer significant production losses due to the presence of this weedy parasite.

Reviewed 1 January 2000