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Effects of Elevated CO2 on Health-Promoting Properties of Broccoli
Schonhof, I., Klaring, H.-P., Krumbein, A. and Schreiner, M. 2007. Interaction between atmospheric CO2 and glucosinolates in broccoli. Journal of Chemical Ecology 33: 105-114.

The authors introduce their study by noting that the glucosinolates found in broccoli comprise a group of bioactive compounds that are responsible for many physiological effects, including serving as feeding deterrents and protective compounds that help protect the plants against herbivore attack (Mewis et al., 2005), enhancing flavor for human consumers, and - perhaps most important of all - helping to prevent cancer in those who consume them (Mikkelsen et al., 2002).

What was done
In a set of three experiments conducted in a controlled greenhouse environment, Schonhof et al. grew well watered and fertilized broccoli (Brassica oleracea var. italica Plenck) cv Marathon plants in large soil-filled containers at ambient (430-480 ppm) and elevated (685-820 ppm) atmospheric CO2 concentrations to the stage where fully developed heads could be harvested for glucosinolate analyses.

What was learned
The roughly 65% increase in atmospheric CO2 concentration increased the fresh weight of the broccoli heads by approximately 7%, while it increased the total glucosinolate concentration of the broccoli inflorescences by 14%, due primarily to identical 37% increases in two methylsulfinylalkyl glucosinolates: glucoiberin and glucoraphanin.

What it means
In a succinct concluding statement, Schonhof et al. say that atmospheric CO2 enrichment "can enhance the health-promoting quality of broccoli because of induced glucosinolate content changes."

Mewis, I., Appel, H.M., Hom, A., Raina, R. and Schultz, J.C. 2005. Major signaling pathways modulate Arabidopsis thaliana (L.) glucosinolate accumulation and response to both phloem feeding and chewing insects. Plant Physiology 138: 1149-1162.

Mikkelsen, M.D., Petersen, B., Olsen, C. and Halkier, B.A. 2002. Biosynthesis and metabolic engineering of glucosinolates. Amino Acids 22: 279-295.

Reviewed 2 May 2007