Making plant methane formation visible-Insights from application of 13 C-labeled dimethyl sulfoxide.

Methane (CH 4 ) formation by vegetation has been studied intensively over the last 15 years. However, reported CH 4 emissions vary by several orders of magnitude, thus making global estimates difficult. Moreover, the mechanism(s) for CH 4 formation by plants is (are) largely unknown.Here, we introduce a new approach for making CH 4 formation by plants clearly visible. By application of 13 C-labeled dimethyl sulfoxide (DMSO) onto the leaves of tobacco plants ( Nicotiana tabacum ) and Chinese silver grass ( Miscanthus sinensis ) the effect of light and dark conditions on CH 4 formation of this pathway was examined by monitoring stable carbon isotope ratios of headspace CH 4 (δ 13 C-CH 4 values).Both plant species showed increasing headspace δ 13 C-CH 4 values while exposed to light. Higher light intensities increased CH 4 formation rates in N. tabacum but decreased rates for M. sinensis . In the dark no formation of CH 4 could be detected for N. tabacum , while M. sinensis still produced ~50% of CH 4 compared to that during light exposure.Our findings suggest that CH 4 formation is clearly dependent on light conditions and plant species and thus indicate that DMSO is a potential precursor of vegetative CH 4 . The novel isotope approach has great potential to investigate, at high temporal resolution, physiological, and environmental factors that control pathway-specific CH 4 emissions from plants.