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

The original report that plants emit methane (CH4 ) under aerobic conditions caused much debate and controversy. Critics questioned experimental techniques, possible mechanisms for CH4 production and the nature of estimating global emissions. Several studies have now confirmed that aerobic CH4 emissions can be detected from plant foliage but the extent of the phenomenon in plants and the precise mechanisms and precursors involved remain uncertain.

Global methane emission estimates from ultraviolet irradiation of terrestrial plant foliage.

*Several studies have reported in situ methane (CH(4)) emissions from vegetation foliage, but there remains considerable debate about its significance as a global source. Here, we report a study that evaluates the role of ultraviolet (UV) radiation-driven CH(4) emissions from foliar pectin as a global CH(4) source. *We combine a relationship for spectrally weighted CH(4) production from pectin with a global UV irradiation climatology model, satellite-derived leaf area index (LAI) and air temperature data to estimate the potential global CH(4) emissions from vegetation foliage.

Reactive oxygen species in aerobic methane formation from vegetation.

The first report of aerobic methane emissions from vegetation by an unknown mechanism suggested that this potential new source may make a significant contribution to global methane emissions. We recently investigated possible mechanisms and reported experiments in which UV-irradiation caused methane emissions from pectin, a major plant cell wall polysaccharide. Our findings also suggest that UV-generated reactive oxygen species (ROS) release methane from pectin.

The role of ultraviolet radiation, photosensitizers, reactive oxygen species and ester groups in mechanisms of methane formation from pectin.

Ultraviolet (UV) radiation has recently been demonstrated to drive an aerobic production of methane (CH(4)) from plant tissues and pectins, as do agents that generate reactive oxygen species (ROS) in vivo independently of UV. As the major building-blocks of pectin do not absorb solar UV found at the earth's surface (i.e.

Ultraviolet radiation drives methane emissions from terrestrial plant pectins.

Recent studies demonstrating an in situ formation of methane (CH(4)) within foliage and separate observations that soil-derived CH(4) can be released from the stems of trees have continued the debate about the role of vegetation in CH(4) emissions to the atmosphere. Here, a study of the role of ultraviolet (UV) radiation in the formation of CH(4) and other trace gases from plant pectins in vitro and from leaves of tobacco (Nicotiana tabacum) in planta is reported. Plant pectins were investigated for CH(4 )production under UV irradiation before and after de-methylesterification and with and without the singlet oxygen scavenger 1,4-diazabicyclo[2.