Nitrification by plants that also fix nitrogen

Abstract

Nitrification is a key stage in the nitrogen cycle; it enables the transformation of nitrogen into an oxidized, inorganic state. The availability of nitrates produced by this process often limits primary productivity and is an important determinant in plant community ecology and biodiversity. Chemoautotrophic prokaryotes are recognized as the main facilitators of this process, although heterotrophic nitrification by fungi may be significant under certain conditions. However, there has been neither biochemical nor ecological evidence to support nitrification by photoautotrophic plants. Here we show how certain legumes that accumulate the toxin, 3-nitropropionic acid, generate oxidized inorganic nitrogen in their shoots, which is returned to the soil in their litter. In nitrogen-fixing populations this 'new' nitrate and nitrite can be derived from the assimilation of nitrogen gas. Normally, the transformation of elemental nitrogen from the atmosphere into a fixed oxidized form (as nitrate) is represented in the nitrogen cycle as a multiphasic process involving several different organisms. We show how this can occur in a single photoautotrophic organism, representing a previously undescribed feature of this biogeochemical cycle.

Plant Bioactive Metabolites and Drugs Produced by Endophytic Fungi of Spermatophyta

“…Analogous for its effects in livestock intoxication, 3-nitropropionic acid (NPA) is a secondary metabolite involved in the nitrification process in Leguminosae [334], particularly of the genera Hippocrepis, Lotus, Scorpiurus and Securigera, and the species Astragalus falcatus and Coronilla viminalis [335]. The fact that the latter are the only species in the respective genera to be reported to produce this compound has raised the interrogative if it is actually produced by associated endophytic microrganinsms.…”

Nitrogen isotopic composition of plant-soil in the Loess Plateau and its responding to environmental change

“…In mountainous areas of France, the δ 15 N value of plant and soil declines with increasing elevation, which is explained as a result of a decrease in temperature and an increase in precipitation increasing with elevation [9] . However, soil nitrogen isotope composition has shown to have complex relations with the environmental change, as well as plant growth mechanism, organic matters translation and the other nitrogen biogeochemistry processes [10][11][12][13] . These complications certainly cause difficulty to use nitrogen isotopes in the environmental change research.…”

Variations in nitrogen isotopic values among various particle-sized fractions in modern soil in northwestern China

“…(1) roots play an important role in soil organic matter in the below-ground ecosystem (Hendricks et al, 2000;Högberg et al, 2001;Neff et al, 2002;Hipkin et al, 2004); (2) leaf-root differences in the δ 15 N values are small, ranging from 0.30‰ to -0.169‰; therefore, nitrogen isotopes associated with the plant roots have the same climatic significance as in the above-plants (Garten, 1993;Robinson et al, 1998;Dijkstra et al, 2003); (3) at the same site, the δ 15 N values of plants from above-ground are different in different parts of plants (Handley et al, 1999), so it is not easy to know δ 15 N values all plants contributed to soil. But the δ 15 N values of below-ground roots (including plant litter) in surface soil can integrate information about nitrogen isotopes from both above-ground and below-ground ecosystems for contributing to soil organic matter.…”