Non-microbial methane emissions from fresh leaves: Effects of physical wounding and anoxia

Non-microbial methane (CH4) emissions from plants might be widespread in nature. However, this unexpected source and its global strength still remain controversial. Very recently it has been suggested that CH4 release by plants may be linked to environmental stress. Using fresh leaves of 73 plants, including those from trees, shrubs and herbaceous species, a series of laboratory experiments have been employed to quantify CH4 emissions and to examine the effect of physical wounding and anoxia. Approximately half of the plants investigated emitted CH4 at rates ≥0.2 ng gdw−1h−1. Emissions from detached intact fresh leaves were in the ranges of 0.20–2.25 and 0.38–2.14 ng gdw−1h−1 when incubated under air and anoxic conditions, respectively. Strongly enhanced emissions were monitored when leaves were physically wounded and/or incubated under anoxia. Several experiments were conducted to verify in-situ emissions of CH4 and exclude microbial activity as the source. Average short-lived pulsed CH4 emissions of 53.4 ng gdw−1h−1, with a range of 0–687 ng gdw−1h−1, were observed from ground fresh leaves of the 60 plant species investigated, indicating that pulse emissions from plants immediately following environmental stress such as wounding need consideration to constrain global CH4 emissions from vegetation. This type of emission may also assist with the delineation of the mechanism involved in non-microbial CH4 formation.

► Methane emissions were investigated from fresh leaves of plants.
► The emissions were strongly enhanced by physical wounding and anoxia.
► The emissions were confirmed to be non-microbial.
► Pulse emissions immediately following environmental stress were important.