EFFECTS OF VESICULAR-ARBUSCULAR MYCORRHIZA ON 14C AND 15N DISTRIBUTION IN NODULATED FABABEANS

Abstract

A two-compartment growth chamber in which the aboveground plant materials were exposed to 14CO2 and the belowground portion was exposed to 15N2 under normal atmospheric pressure was designed for carbon and nitrogen transfer studies. Vicia faba infected with vesicular-arbuscular fungus Glomus mossae and non-mycorrhizal plants fixed similar quantities of N2 at an age of 6½ wk. Approximately 0.10 mg N was fixed∙g−1 dry plant materials∙day−1 and 40 mg C∙g−1 dry matter day−1 were synthesized by mycorrhizal and non-mycorrhizal fababeans during 48 h exposure to 14CO2 at 6½ wk with no apparent difference in yield of dry matter. The non-mycorrhizal plants transferred 37% of the fixed 14C beneath ground. The mycorrhizal ones transferred 47% of the fixed 14C beneath ground. Most of the difference could be accounted for in the belowground respiration. The 14CO2 produced by root-microbial systems of the mycorrhizal fababeans was twice as great as that of the nonmycorrhizal; both contained active rhizobium.