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biological nitrogen fixation | fixare a azotului biologic |
nitrogen cycle The complex set of processes by which crops acquire the large amount of nitrogen they need to make proteins, nucleic acids and other biochemicals of which they are composed, and how the nitrogen returns to the atmosphere | ciclu al azotului |
nitrogen dioxide A reddish-brown gas; it exists in varying degrees of concentration in equilibrium with other nitrogen oxides; used to produce nitric acid, NO2 | dioxid de azot |
nitrogen fixation Assimilation of atmospheric nitrogen by a variety of microorganisms which live freely in soil. Once the nitrogen has been captured by one of the microorganisms, there are many different routes by which it is handled. Some is retained in the soil as decomposing plant matter, waiting to be released and taken up by new crops as a nitrate. That nitrate is produced by nitrifying bacteria living in the soil that thrive on ammonia, which is produced by decaying plant and animal material. In processing nitrogen the nitrifying bacteria produce nitrate that can be absorbed by the roots of plants | fixare a azotului |
nitrogen monoxide A colourless gas, soluble in water, ethanol and ether. It is formed in many reactions involving the reduction of nitric acid, but more convenient reactions for the preparation of reasonably pure NO are reactions of sodium nitrite, sulphuric acid, etc. | monoxid de azot |
nitrogen oxide | oxid de azot |
nitrogen oxide A colorless gas that, at room temperature, reacts with oxygen to form nitrogen dioxide; may be used to form other compounds, NOx | oxid de azot |
nitrogen oxides Oxides formed and released in all common types of combustion; they are formed by the oxidation of atmospheric nitrogen at high temperatures. Introduced into the atmosphere from car exhausts, furnace stacks, incinerators, power stations and similar sources, the oxides include nitrous oxide, nitric oxide, nitrogen dioxide, nitrogen pentoxide and nitric acid. The oxides of nitrogen undergo many reactions in the atmosphere to form photochemical smog | oxizi de azot |
nitrogen trifluoride | trifluorură de azot |
organic nitrogen Essential nutrient of the food supply of plants and the diets of animals. Animals obtain it in nitrogen-containing compounds, particularly aminoacids. Although the atmosphere is nearly 80% gaseous nitrogen, very few organisms have the ability to use it in this form. The higher plants normally obtain it from the soil after microorganisms have converted the nitrogen into ammonia or nitrates, which they can then absorb. This conversion of nitrogen, known as nitrogen fixation, is essential for the formation of amino acids which, in turn, are the building blocks of proteins | azot organic |