How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Photosynthetic Acclimation to Elevated CO2 and Low Nitrogen Supply in Soybean
Sims, D.A., Luo, Y. and Seeman, J.R.  1998.  Comparison of photosynthetic acclimation to elevated CO2 and limited nitrogen supply in soybean.  Plant, Cell and Environment 21: 945-952.

What was done
Soybeans were grown in environmental chambers subjected to atmospheric CO2 concentrations of 350 and 700 ppm.  In addition, one-half of the soybeans received adequate levels of nitrogen fertilization, while the other half received one-tenth of the normal amount.  Thus, this setup enabled the authors to study the effects of elevated CO2 and nitrogen availability on photosynthesis in this species.

What was learned
Both elevated CO2 and low nitrogen caused reductions in leaf rubisco content and leaf photosynthetic capacity.  Although these phenomena lowered leaf nitrogen content as a percentage of total leaf dry mass, only low nitrogen caused significant reductions in leaf nitrogen as a percentage of total leaf structural dry mass.  Thus, elevated CO2 did not decrease photosynthetic capacity by reducing the amount of leaf nitrogen, but rather by causing the accumulation of nonstructural carbohydrates, thus triggering photosynthetic end-product feedback inhibition.

What it means
The results of this study suggest that photosynthetic acclimation to elevated CO2 in soybean is not caused by reductions in leaf nitrogen content, but rather by the accumulation of foliar non-structural carbohydrates that can cause feedback inhibition of primary production.

Reviewed 15 July 1999