How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Persistent Effects of Early CO2 Enrichment on Winter Wheat
Ulman, P., Catsky, J. and Pospisilova, J.  2000.  Photosynthetic traits in wheat grown under decreased and increased CO2 concentration, and after transfer to natural CO2 concentration.  Biologia Plantarum 43: 227-237.

What was done
The authors grew winter wheat (Triticum aestivum L. cv. Zdar line A) in environmental chambers receiving atmospheric CO2 concentrations of 150, 350, and 800 ppm for 18 days post-germination.  Thereafter, all seedlings were transferred to chambers receiving air containing 350 ppm CO2 and grown for another 22 days to determine if there were any holdover effects of the sub-ambient and super-ambient CO2 concentrations on photosynthesis and growth in this important cereal crop.

What was learned
Photosynthetic rates of sub-ambiently-grown seedlings measured 12 to 22 days after transfer to 350 ppm CO2 tended to be greater than those displayed by control plants raised exclusively at 350 ppm CO2, while seedlings grown at 800 ppm CO2 and transferred to 350 ppm CO2 exhibited photosynthetic rates that tended to be lower than those observed in the control seedlings.  Nevertheless, seedlings initially grown at elevated CO2 concentrations attained whole plant dry mass values that were 14% greater than those reached by control plants, while seedlings initially grown at the subambient CO2 concentration attained values that were 24% lower than those measured in control seedlings.

What it means
These data indicate that early exposure of wheat seedlings to elevated CO2 concentrations can lead to positive effects that may persist long after the cessation of CO2 enrichment.  Indeed, although photosynthetic rates of CO2-enriched plants were suppressed relative to values observed in control plants upon transfer to air containing 350 ppm CO2, the previously-enriched plants still produced more overall biomass than seedlings grown in the other CO2 treatments, due to the initial growth stimulation provided by atmospheric CO2 enrichment that must have occurred early in their ontogeny.  Thus, commercial growers who utilize greenhouses and other enclosures in their operations might profitably consider enriching the air around their crops with CO2 for a short period of time after germination to stimulate their initial growth and increase the ultimate yield produced.

Reviewed 14 August 2002