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Soybean Photosynthesis: Elevated CO2 vs. High Temperatures and Ozone Concentrations
Reference
Mishra, S., Heckathorn, S.A., Barua, D., Wang, D., Joshi, P., Hamilton III, E.W. and Frantz, J. 2008. Interactive effects of elevated CO2 and ozone on leaf thermotolerance in field-grown Glycine max. Journal of Integrative Plant Biology 50: 1396-1405.

What was done
Working at the SoyFACE facility of the University of Illinois (USA), the authors studied the positive impact of atmospheric CO2 enrichment on the photosynthetic rates of field-grown soybean (Glycine max L.) plants experiencing the simultaneous negative effects of acute heat stress and elevated atmospheric ozone (O3) concentrations.

What was learned
Mishra et al. report that elevated O3 exacerbated heat-related decreases in photosynthetic electron transport, thereby providing a double whammy to the plants, but they say that "elevated CO2 minimized or prevented light-dependent O3-related decreases in electron transport (and thus photoinhibition) during heat stress."

What it means
The seven scientists who conducted the work conclude that "protection of photosynthesis during heat stress by elevated CO2 occurs in field-grown soybean under ambient O3," and that elevated CO2 also "limits heat damage under elevated O3," most likely as a result of "decreased photorespiration and stomatal conductance." Hence, it can be appreciated that the ongoing rise in the air's CO2 content provides valuable protection against two very common environmental stresses that might otherwise deal a devastating blow to the ability of the plants to properly grow and produce profitable yields.

Reviewed 31 December 2008