nitrogen fixation

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ni·tro·gen fix·a·tion

process in which atmospheric nitrogen is converted to ammonia.
Farlex Partner Medical Dictionary © Farlex 2012

nitrogen fixation

n.
1. The conversion of atmospheric nitrogen into compounds, such as ammonia, by natural agencies or various industrial processes.
2. The conversion by certain soil microorganisms, such as rhizobia, of atmospheric nitrogen into compounds that plants and other organisms can assimilate.

ni′tro·gen-fix′er (-fĭk′sər) n.
ni′tro·gen-fix′ing adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

nitrogen fixation

the utilization of atmospheric nitrogen in the synthesis of AMINO ACIDS by some bacteria. Such bacteria can be free-living (e.g. Azotobacter, an aerobe; Clostridium, an obligate anaerobe) while others (e.g. Rhizobium) live in association with plants, occupying swellings in the root called root nodules. The latter relationship is one of SYMBIOSIS, in that the plant gains nutrients and thus can live in nitrogen-poor soils, while the nitrogen-fixer obtains a supply of carbohydrates from the plant. The nitrogen is reduced to ammonia in the microbes by action of the enzyme nitrogenase: N2 + 3 H22 NH3, the ammonia then reacting with keto acids to form amino acids.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
References in periodicals archive ?
We chose species from four groups defined by traits that are potentially relevant to nutrient cycling: (1) early-season annual forbs, (2) late-season annual forbs, (3) perennial bunchgrasses, and (4) nitrogen-fixers. Though defined here primarily by their phenology (except for N-fixers), these groups also differ in other characteristics relevant to nutrient retention and turnover, including rooting depth, root-to-shoot ratio, competitive ability on fertile and infertile sites, size, and foliage C/N ratio (Gulmon et al.
They found them for the first time as deep as 450 feet, changing the way scientists thought about how deep these nitrogen-fixers are distributed.
He found that nitrogen-fixers, for instance, realized lower proficiency in the resorption of nitrogen.
Fiber crops like kenaf, hemp, and sisal are nitrogen-fixers, valuable for crop rotation as well as for their pulp.
They can use it in selecting legumes in the greenhouse or field that are superior nitrogen-fixers in the face of stress.