The study suggests plant leaves account for less than 1% of methane
Plants remain "an effective way" of tackling global warming despite emitting small amounts of a greenhouse gas, a study has shown.
The Edinburgh University research suggests plant leaves account for less than 1% of Earth's methane emissions.
The impact on global warming from methane is considered to be about 25 times greater than from carbon dioxide.
A previous study suggested plants were responsible for producing large amounts of methane.
Scientists said the findings confirmed that trees are a useful way of offsetting greenhouse gas emissions, as their output of small amounts of methane is "far outweighed by their capacity to store carbon" from the atmosphere in their leaves, wood and bark.
During the study the scientists created artificial leaves made from plant pectin and measured the methane produced when the leaves were exposed to sunlight.
They combined their results with satellite data on the leaf coverage of the Earth's surface, ozone in the atmosphere, cloud cover, temperature, and information on sunshine levels, to help work out the amount of methane produced by all plants on Earth.
Dr Andy McLeod, of Edinburgh University's school of geosciences, said: "Our results show that plant leaves do give rise to some methane, but only a very small amount.
"This is a welcome result as it allays fears that forestry and agriculture were contributing unduly to global warming."
The research, carried out in collaboration with the National Centre for Atmospheric Research in the US, was funded by the Natural Environment Research Council and Forest Research, and is published in the journal New Phytologist.