Greenhouse Gases May Have Changed Photosynthesis of Plants Over the 20th Century

Increased CO2 concentrations in the atmosphere may have actually altered the photosynthesis of plants over the 20^th century. Scientists have found that plants' photosynthetic metabolism has changed over this time period.

In most plants, the uptake of CO2 through photosynthesis is reduced by a side reaction called photorespiration. The researchers have now found that the CO2 increase in the atmosphere over the 20^th century has shifted the balance between photosynthesis and photorespiration toward photosynthesis. This shift, in particular, has contributed to the global vegetation's ability to dampen climate change by absorbing a third of human-caused CO2 emissions.

The photorespiration pathway is known to increase with temperature. This means that temperature and CO2 effects predictably oppose one another, which means that the CO2-driven metabolic shift will be counteracted by future temperature increases.

Vegetation's ability to capture CO2 from the atmosphere through photosynthesis is not only a decisive factor for the global CO2 balance, but also in predicting future climate change and crop productivity. By monitoring plant metabolism using historic plant samples, researchers can quantify how much increased atmospheric CO2 levels during the 20^th century have contributed to plants' ability to capture carbon dioxide.

"Until recently, studying how plants respond to increases in CO2 on decadal to centennial time scales has relied on simulations based on short-term experiments, because methods to detect long-term metabolic changes were not available," said Jurgen Schleucher, one of the researchers, in a news release. "By reconstructing past metabolic shifts in response to environmental changes, we lay the foundation for better modeling of future plant performance."

The findings reveal that as temperatures rise, plants may lose the ability to dampen CO2 emissions as much over time.  This is important to note as climate change continues.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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