Writing in the Royal Society journal Proceedings B, a University of Cambridge group led by Ellen Nisbet says that under normal circumstances, plants convey methane from the soil to the air, rather than actually producing it.
Concentrations of methane in the atmosphere appear to be increasing after several years of stable levels, and the scientists suggest that identifying sources of the potent gas is a key to climate control.
Experiments conducted by Nisbet’s group showed that, in her words, "the vast majority of methane emitted in normal growth conditions is explained by the absorption of methane in the soil water".
The 2006 study, by a group from the Max Planck Institute for Chemistry in Mainz, Germany, found that plants emitted methane from their leaves under normal growing conditions. In high sunlight and temperatures, however, the gas output increased. The German team suggested that plants have a biochemical pathway that could generate the gas — and the researchers are actively looking for it.
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