Nature: Plants cannot make methane, say researchers seeking to resolve a mystery that has puzzled biologists for several years. Instead, they believe, plants simply take up the gas dissolved in water from the soil, and pass it back out through their leaves. Three years ago, a European team reported that 10–30% of Earth’s methane emissions come from plants1. Methane is a powerful greenhouse gas and, if true, the finding would require a major rethink of the planet’s carbon budget. But …