Abstract:According to conventional knowledge, methane emission from natural sources is primarily produced by strictly anaerobic methanogen microbes. However, recent findings suggest that terrestrial plants may also emit methane under aerobic conditions, and this has far-reaching implications for the estimation of global methane budget. The findings are still heavily debated. Some research has shown that plants can emit methane under an aerobic environment, and that compounds like pectin or polygalacturaonic acid, which contain methoxyl groups, and other plant structure components such as cellulose and lignin, can function as precursors for the production of methane. Other researchers argued that methane emission by plant materials were zero or very small in quantity, and the measured methane emissions from plants may come from soil water, which contains dissolved methane and plants emit the dissolved methane into the atmosphere through transpiration, or evaporation. The mechanism for the methane emission from plants under aerobic conditions remains unknown, environmental stress such as light, temperature, UV radiation and physical injury may lead to significant methane emissions from plants, but these factors are still uncertain. Even so, fluxes on the global and regional methane emissions from plants were estimated, and the global estimated values vary between 10 and 236 Tg?a-1. These controversies should be re-examined in independent studies through measuring plant methane emission in different habitats, and examining the mechanisms of methane emissions from plants in the future.