In the above citied letter to Nature the authors concluded out of their experiments: "Here we demonstrate using stable carbon isotopes that methane is readily formed in situ in terrestrial plants under oxic conditions by a hitherto unrecognized process."
Reading their paper it is easily seen that their conclusion is not convincing because their experimental strategy lacks and fails some simple tests to exclude or include known biogenic sources of methane.
At that time common biologic knowledge is: Biogene methanogenesis is performed by archaea, (perhaps some cyanobacteria, fungi and microalgae ) which can be divided into two groups:
– acetate-consumers…..Comment on_keppler.pdfComment on_keppler.pdf