intramolecular oxygen plays a part.
"The Breath of Life"
John Burroughs
Even in the complete absence of atmospheric oxygen the protoplasm may go on breaking down and accumulating various compounds containing relatively much carbon and hydrogen-so-called intramolecular respiration; but in ordinary plants this process soon comes to an end, because the blocking up of the molecular plexus leads to obstruction and interferes with the normal assimilation and dis-assimilation, and, if prolonged, leads to pathological conditions, and eventually death.
"Disease in Plants"
H. Marshall Ward