Nitrogen fixation definition

nitrogen fixation

–noun

1.	any process of combining atmospheric nitrogen with other elements, either by chemical means or by bacterial action: used chiefly in the preparation of fertilizers, industrial products, etc.

2.	this process as performed by certain bacteria found in the nodules of leguminous plants, which make the resulting nitrogenous compounds available to their host plants.

Origin:
1890–95

Dictionary.com Unabridged (v 1.1)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.
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nitrogen fixation
n.

The conversion of atmospheric nitrogen into compounds, such as ammonia, by natural agencies or various industrial processes.
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 (nī'trə-jən-fĭk'sər) n., ni'tro·gen-fix'ing adj.

The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2006 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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nitrogen fixation
noun
the assimilation of atmospheric nitrogen by soil bacteria and its release for plant use on the death of the bacteria

WordNet® 3.0, © 2006 by Princeton University.
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nitrogen fixation

The process by which free nitrogen from the air is combined with other elements to form inorganic compounds, such as ammonium ions, which can then be converted by nitrification into nutrients that can be readily absorbed by plants and other organisms for incorporation into more complex organic compounds. During lighting strikes, the atmosphere's free nitrogen molecules (N₂) are broken apart and combine with oxygen to form nitrogen oxides that dissolve in rain to form nitric acid; atmospheric nitrogen is also fixed industrially under high pressure and heat to form ammonia, as in the production of fertilizers. Many species of cyanobacteria and certain other forms of bacteria, especially those that live in the roots of legumes, conduct nitrogen fixation as part of their metabolism, using the enzyme nitrogenase to combine nitrogen with hydrogen as ammonia. All living organisms are dependent on nitrogen fixation and would ultimately die without it. See more at nitrogen cycle.

The American Heritage® Science Dictionary
Copyright © 2002 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Main Entry: nitrogen fixation
Function: noun
1 : the industrial conversion of free nitrogen into combined forms useful especially as starting materials forfertilizers or explosives
2 : the metabolic assimilation of atmospheric nitrogen by soil microorganisms and especially rhizobia and its release for plant use by nitrification inthe soil on the death of the microorganisms

Merriam-Webster's Medical Dictionary, © 2002 Merriam-Webster, Inc.
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