Effect of UV radiation and temperature on the emission of methane from plant biomass and structural components

Abstract

Abstract.The recently reported finding that plant matter and living plants produce significant amounts of the important greenhouse gas methane under aerobic conditions has led to an intense scientific and public controversy. Whereas some studies question the up-scaling method that was used to estimate the global source strength, others have suggested that experimental artifacts could have caused the reported signals, and two studies, one based on isotope labeling, have recently reported the absence of CH 4 emissions from plants. Here we show -using several independent experimental analysis techniques -that dry and detached fresh plant matter, as well as several structural plant components, emit significant amounts of methane upon irradiation with UV light and/or heating. Emissions from UV irradiation are almost instantaneous, indicating a direct photochemical process. Longtime irradiation experiments demonstrate that the size of the CH 4 producing reservoir is large, exceeding potential interferences from degassing or desorption processes by several orders of magnitude. A dry leaf of a pure 13 C plant produces 13 CH 4 at a similar rate as dry leaves of non-labeled plants produce non-labeled methane.

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).…”

“…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.…”

“…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. The majority of studies reported substantial CH 4 emissions, while Bowling et al (2009) reported no evidence for substantial CH 4 emissions by a conifer forest under high UV radiation, to which a soil CH 4 sink might contribute.…”

“…2). Two other components of plant cell wallsdcellulose and lignindhave been reported to be likely CH 4 sources, even though cellulose does not contain methyl groups (Bruhn et al, 2012;Vigano et al, 2009Vigano et al, , 2008 (Fig. 2).…”

Abiotic methanogenesis from organosulphur compounds under ambient conditions

“…It has been shown that CH 4 can be produced abiotically from plant material by exposing it to ultraviolet (UV) irradiation [15][16][17][18] . A reaction of reactive oxygen species (ROS) with methoxyl groups of pectic polysaccharides was suggested as a possible route to CH 4 formation under UV radiation 19 .…”