Emission of methane, carbon monoxide, carbon dioxide and short‐chain hydrocarbons from vegetation foliage under ultraviolet irradiation

Abstract

The original report that plants emit methane (CH 4) under aerobic conditions caused much debate and controversy. Critics questioned experimental techniques, possible mechanisms for CH 4 production and the nature of estimating global emissions. Several studies have now confirmed that aerobic CH 4 emissions can be detected from plant foliage but the extent of the phenomenon in plants and the precise mechanisms and precursors involved remain uncertain. In this study, we investigated the role of environmentally realistic levels of ultraviolet (UV) radiation in causing the emission of CH 4 and other gases from foliage obtained from a wide variety of plant types. We related our measured emissions to the foliar content of methyl esters and lignin and to the epidermal UV absorbance of the species investigated. Our data demonstrate that the terrestrial vegetation foliage sampled did emit CH 4, with a range in emissions of 0.6–31.8 ng CH 4 g−1 leaf DW h−1, which compares favourably with the original reports of experimental work. In addition to CH 4 emissions, our data show that carbon monoxide, ethene and propane are also emitted under UV stress but we detected no significant emissions of carbon dioxide or ethane.

The global methane budget 2000–2012

“…This pathway was criticized (e.g. Dueck et al, 2007;Nisbet et al, 2009), and although numerous studies have since confirmed aerobic emissions from plants and better resolved its physical drivers (Fraser et al, 2015), global estimates still vary by 2 orders of magnitude meaning any potential implication for the global methane budget remains highly uncertain. Second, plants act as "straws", drawing methane produced by microbes in anoxic soils (Rice et al, 2010;Cicerone and Shetter, 1981).…”

A novel pathway of direct methane production and emission by eukaryotes including plants, animals and fungi: An overview

“…soil or plant water) and whether plants have their own mechanism(s) to produce CH 4 have been debated (Bruhn et al, 2012;Keppler et al, 2009;Nisbet et al, 2009). Evidence is now accumulating to indicate that plants can produce CH 4 even in the presence of oxygen (Bruggemann et al, 2009;Bruhn et al, 2009Bruhn et al, , 2014Cao et al, 2008;Fraser et al, 2015;Keppler et al, 2008;Lenhart et al, 2014;McLeod et al, 2008;Messenger et al, 2009;Mikkelsen et al, 2011;Reid, 2009, 2011;Sanhueza and Donoso, 2006;Sinha et al, 2007;Vigano et al, 2009Vigano et al, , 2008Wang et al, 2009aWang et al, , 2009bWang et al, , 2011aWatanabe et al, 2012;Wishkerman et al, 2011).…”

“…However, clear evidence shows that pectin is not the only precursor (Carmichael et al, 2014;Lenhart et al, 2014;Vigano et al, 2009), and several environmental stresses in addition to UV radiation have been observed to induce CH 4 production. Thus, whether Bloom et al (2010) underestimated the magnitude of this plant source of CH 4 has been a subject of debate (Bruhn et al, 2012;Fraser et al, 2015).…”

“…Accordingly, terrestrial plants are commonly subjected to physical injury. However, the effect of leaf excision on observations of CH 4 emissions by plants is questionable because stomatal closure induced by leaf excision would influence instantaneous measurements of CH 4 emissions (Fraser et al, 2015).…”

“…The impacts of UV radiation and heating on CH 4 emissions from detached leaves (Bruhn et al, 2009;Fraser et al, 2015;McLeod et al, 2008;Reid, 2009, 2011;Vigano et al, 2009Vigano et al, , 2008Wang et al, 2011b), intact plants and structural components (e.g. pectin, lignin, cellulose and leaf surface wax) (Bruhn et al, 2014;Keppler et al, 2008;McLeod et al, 2008;Messenger et al, 2009;Vigano et al, 2009Vigano et al, , 2008 have been extensively tested.…”