The role of methane in plant physiology: a review

Methane (CH 4 ), one of the most important greenhouse gases, has conventionally been considered as a physiologic inert gas. However, this perspective has been challenged by the observation that CH 4 has diverse biological functions in animals, such as anti-inflammatory, antioxidant, and anti-apoptosis. Meanwhile, it has now been identified as a possible candidate of gaseous signaling molecule in plants, although its biosynthetic and metabolic pathways as well as the mechanism(s) of CH 4 signaling have not fully understood yet. This paper aims to review the available evidence for the biological roles of CH 4 in regulating plant physiology. Although currently available reports do not fully support the notion of CH 4 as a gasotransmitter, they do show that CH 4 might be produced by an aerobic, non-microbial pathway from plants, and plays important roles in enhancing plant tolerance against abiotic stresses, such as salinity, drought, heavy metal exposure, and promoting root development, as well as delaying senescence and browning. Further results showed that CH 4 could interact with reactive oxygen species (ROS), other gaseous signaling molecules [e.g., nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H 2 S)], and glutathione (GSH). These reports thus support the idea that plant-produced CH 4 might be a component of a survival strategy of plants. Finally, the possibility of CH 4 application in agriculture is preliminarily discussed.