nitrogen cycle


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ni·tro·gen cy·cle

the series of events in which the nitrogen of the atmosphere is fixed, thus made available for plant and animal life, and is then returned to the atmosphere: nitrifying bacteria convert N2 and O2 to NO2- and NO3-, the latter being absorbed by plants and converted to protein; if plants decay, the nitrogen is in part given up to the atmosphere and the remainder is converted by microorganisms to ammonia, nitrites, and nitrates; if the plants are eaten, the animals' excreta or bacterial decay return the nitrogen to the soil and air.

nitrogen cycle

n.
The circulation of nitrogen in nature, consisting of a cycle of chemical reactions in which nitrogen from the atmosphere is fixed in compounds in soil or water, assimilated by plants and animals, released to the soil and water through decomposition, and returned to the atmosphere through denitrification.

nitrogen cycle

Etymology: Gk, nitron, soda, genein, to produce, kyklos, circle
the circulation of nitrogen through natural processes in either of two ways: from the soil to organisms that excrete nitrogen products back into the soil or by bacterial fixation of atmospheric nitrogen through other organisms that decay and release the element back into the atmosphere.

ni·tro·gen cy·cle

(nī'trŏ-jĕn sī'kĕl)
The series of events in which the nitrogen of the atmosphere is fixed, thus made available for plant and animal life, and is then returned to the atmosphere: nitrifying bacteria convert N2 and O2 to NO2- and NO3-, the latter being absorbed by plants and converted to protein; if plants decay, the nitrogen is in part given up to the atmosphere and the remainder is converted by microorganisms to ammonia, nitrites, and nitrates; if the plants are eaten, the animals' excreta or bacterial decay return the nitrogen to the soil and air.
Nitrogen cycleclick for a larger image
Fig. 229 Nitrogen cycle .

nitrogen cycle

the circulation of nitrogen in the environment as a result of the activity of living organisms. 80% of the atmosphere is made up of nitrogen and this is maintained by the balancing action of the cycle.
References in periodicals archive ?
Given the current dramatic rate of change in the ocean nitrogen cycle the researchers are not sure how long it will take for marine ecosystems to adapt.
The gate-keepers to the biological part of the nitrogen cycle are certain micro-organisms capable of fixing elemental atmospheric nitrogen.
The North Pacific is so vast it is hard to imagine that humans could impact the natural nitrogen cycle.
It shows how the availability of nitrate, and feedbacks within the global nitrogen cycle, would have controlled the shifting of the oceans between the two oxygen-free states - potentially restricting the spread of early complex life.
The role legumes can play in reducing excess nitrogen in the nitrogen cycle is not widely recognized," says Russelle, who is in the ARS Plant Science Research Unit at St.
Arboreal emissions of nitrogen oxides are "evidently an important component of the nitrogen cycle," Hari says.
Nitrogen transformation and nitrate leaching in the nitrogen cycle have been suggested to be major causes of soil acidification (Bolan et al.
According to Srini Kambhampati, professor and chair of the biology department at the University of Texas at Tyler, the disappearance of cockroaches would play havoc with the nitrogen cycle.
Nitrous oxide, an important greenhouse gas, is a product of the nitrogen cycle and can be produced by combustion of biofuels.
Summary: TEHRAN (FNA)- Scientists braved ticks and a tiger to discover how human activities have perturbed the nitrogen cycle in tropical forests.