METABOLISM OF MANNITOL IN HIGHER PLANTS

Abstract

To determine to what extent higher plants can metabolize mannitol‐C 14 , it was introduced into 26 species belonging to 17 families. Fifteen species respired mannitol as measured by the evolution of C 14 O 2 . In several species, including Fraxinus americana and Syringa vulgaris, mannitol was respired at rates comparable to those of fructose and glucose. In others, including Avena sativa, mannitol was respired only slightly. A lag period in the production of C 14 O 2 from mannitol‐C 14 , which does not occur after offering glucose‐C 14 or fructose‐C 14 , was considered to be due to a slow penetration of mannitol to the site of its metabolism. The first step in the dissimilation of mannitol was shown to be its oxidation to fructose, possibly via phosphorylated intermediates. Mannitol was not found to be a constituent of polysaccharides of Syringa vulgaris.