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.