Part II of "Matter cycles": The nitrogen cycleNitrogen is a part of vital organic compounds in microrganisms, such as amino acids, proteins and DNA. The gaseous form of nitrogen (N2), makes up 78% of the troposphere. One might think this means we always have plenty of nitrogen available, but unfortunately it does not work that way. Nitrogen in the gaseous form cannot be absorbed and used as a nutrient by plants and animals; it must first be converted by nitrifying bacteria, so that it can enter food chains as a part of the nitrogen cycle. Show
During the conversion of nitrogen cyano bacteria will first convert nitrogen into ammonia and ammonium, during the nitrogen fixation process. Plants can use ammonia as a nitrogen source. Nitrogen fixation is carried out according to the following reaction: After ammonium fixation, the ammonia and ammonium that is formed will be transferred further, during the nitrification process. Aerobic bacteria use oxygen to convert these compounds. Nitrosomonas bacteria first convert nitrogen gas to nitrite (NO2-) and subsequently nitrobacter convert nitrite to nitrate (NO3-), a plant nutrient.
Nitrification is carried out according to the following reactions: Plants absorb ammonium and nitrate during the assimilation process, after which they are converted into nitrogen-containing organic molecules, such as amino acids and DNA. Denitrification is carried out
according to the following reaction: Finally, nitrogen is released into the atmosphere again. The whole process starts over after release. A schematic representation of the nitrogen cycle is shown here: Nitrogen as a limiting factorAlthough the nitrogen conversion processes often occurs and large quantities of plant nutrients are produced, nitrogen is often a limiting factor for plant growth. Water flowing across the soil causes this error. Nitrogen nutrients are water-soluble and as a result they are easily drained away, so that they are no longer available for plants. The annamox reaction In 1999 researchers at the Gist-Brocades in Delft, The Netherlands, discovered a new reaction to be added to the nitrogen cycle; the so-called annamox reaction. This is now found to occur in the Black Sea, as well. The reaction implies conversion of nitrite and ammonium to pure nitrogen gas (N2), which than escapes to the atmosphere. The reaction mechanism is triggered by a newly discovered bacterium, called Brocadia anammoxidans. This appears to be a compartmentalized bacterium; within the cell membrane two compartments can be found which are also surrounded by a membrane, a very rare phenomenon. Intermediate products of the reaction included hydroxylamine, and toxic hydrazine compounds. The bacterial membranes were found to consists of badly permeable membranes, which are thought to function as a barrier for hydrazines produced within the cell. This discovery has major consequences, as it alters the entire contribution of oceans to the nitrogen balance. Source: NRC Handelsblad, 12-04-2003 For more information on nitrogen, move to the periodic chart Back to main page of matter cycles To the matter cycles pollution page Nutrients in irrigation water About LenntechLenntech (European Head Office) Distributieweg 3 Lenntech USA LLC (Americas) 5975 Sunset Drive Lenntech DMCC (Middle East) Level 6 - OFFICE #101-One
JLT Tower Copyright © 1998-2022 Lenntech B.V. All rights reserved What converts nitrogen from the air into a form plants can use?Fixation converts nitrogen in the atmosphere into forms that plants can absorb through their root systems. A small amount of nitrogen can be fixed when lightning provides the energy needed for N2 to react with oxygen, producing nitrogen oxide, NO, and nitrogen dioxide, NO2.
Which of the following can convert nitrogen in the air into a form plants can use a bacteria B fungi C protists D animals?Nitrogen-fixing bacteria are prokaryotic microorganisms that are capable of transforming nitrogen gas from the atmosphere into “fixed nitrogen” compounds, such as ammonia, that are usable by plants.
Which of the following can convert nitrogen in the air?A noteworthy and very important feature of Azotobacter and Nitrobacter are their ability to "fix" atmospheric nitrogen, by the conversion of this elemental form to ammonia.
What forms of nitrogen can plants use?Nitrate is the form of nitrogen most used by plants for growth and development. Nitrate is the form that can most easily be lost to groundwater. Ammonium taken in by plants is used directly in proteins. This form is not lost as easily from the soil.
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