Nitrogen fixation and nitrate reduction in the root nodules of legumes

Abstract

Published data on, and hypotheses regarding the effect of NO−3 on functioning of legume root nodules are reviewed. It is concluded that a short‐term reversible effect of NO−3 may act via an increased resistance to O2 diffusion in nodules; this is coupled to decreased bacteroid respiration. For longer exposures to NO−3 nodule activity is irreversibly lost, but how this relates to carbohydrate deprivation or NO‐2 accumulation is unclear. Complicating factors include denitrification reactions and the interaction of NO−2 with leghaemoglobin.

Development of environmental friendly bioinoculate for peanut (Arachis hypogea L.) production in Eastern Ethiopia

“…On top of this, all tested Bradyrhizobium inoculation including inorganic N application significantly increased the grain yield of peanut at Fedis and Babile sites. The positive effect of N application might be associated the presence of low concentration of nitrate in both soils which could act as an additional source of nitrogen until the plant start N 2 fixation (Becana and Sprent 1987). However, the result showed that yield increases with inorganic N application was not statistically at par with HUGNR-29 inoculation, implying that Rhizobium inoculation can substitute the external inorganic N application.…”

Rapid and reversible nitrate inhibition of nodule growth and N2fixation activity in soybean (Glycine max(L.) Merr.)

“…It is generally recognized that N2 fixation in the nodules requires more energy than nitrate assimilation in the roots. If plants have adapted to conserve their energy, they should be able to detect the presence and level of nitrate in the rooting medium (Becana and Sprent 1987). Therefore, it is assumed that the nodule growth and nitrogen fixation activity in soybean may sensitively respond to the external nitrate level possibly through sensing of the internal nitrate concentration in roots and / or nodules.…”

Nitrogen content in plant biomass from subterranean clover (Trifolium subterraneum L.) and cocksfoot (Dactylis glomerata L.) grown under different inorganic nitrogen supply

“…Increase in the mixtures with subterranean clover was considerable reaching 138.6% on account of the legume component. It is known that higher amounts of nitrogen in the soil inhibit processes of nodule formation and nitrogen fixation in legume plants (Streeter 1985a, 1985b, Becana & Sprent 1987, Streeter 1993. A dynamic relationship exists between legume and grass component of the mixture in which absorption of soil nitrogen by the grasses reduces its inhibiting effect on nitrogen fixation.…”