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Nitrogen is a fundamental nutrient in agriculture, playing a crucial role in plant growth and development. It is an essential component of proteins, enzymes, chlorophyll, and nucleic acids, all of which are essential for various metabolic processes within plants. [2]
A large body of research has shown that AM fungi can, and do, transfer nitrogen to plants and transfer nitrogen between plants, including crop plants. However, it has not been shown conclusively that there is a growth benefit from AM due to nitrogen. Some researchers doubt that AM contribute significantly to plant N status in nature. [12]
Most of the nitrogen taken up by plants is from the soil in the forms of NO − 3, although in acid environments such as boreal forests where nitrification is less likely to occur, ammonium NH + 4 is more likely to be the dominating source of nitrogen. [49] Amino acids and proteins can only be built from NH + 4, so NO − 3 must be reduced.
Nitrogen assimilation is the formation of organic nitrogen compounds like amino acids from inorganic nitrogen compounds present in the environment. Organisms like plants , fungi and certain bacteria that can fix nitrogen gas (N 2 ) depend on the ability to assimilate nitrate or ammonia for their needs.
Within legume root nodules, nitrogen gas (N 2) from the atmosphere is converted into ammonia (NH 3), which is then assimilated into amino acids (the building blocks of proteins), nucleotides (the building blocks of DNA and RNA as well as the important energy molecule ATP), and other cellular constituents such as vitamins, flavones, and hormones.
Nitrogen is the most critical element obtained by plants from the soil, to the exception of moist tropical forests where phosphorus is the limiting soil nutrient, [36] and nitrogen deficiency often limits plant growth. [37] Plants can use nitrogen as either the ammonium cation (NH 4 +) or the anion nitrate (NO 3 −).
Plants that contribute to nitrogen fixation include those of the legume family—Fabaceae— with taxa such as kudzu, clover, soybean, alfalfa, lupin, peanut and rooibos. [45] They contain symbiotic rhizobia bacteria within nodules in their root systems, producing nitrogen compounds that help the plant to grow and compete with other plants. [58]
[52] [53] Nitrogen gases and aerosols can be directly toxic to certain plant species, affecting the aboveground physiology and growth of plants near large point sources of nitrogen pollution. Changes to plant species may also occur as nitrogen compound accumulation increases availability in a given ecosystem, eventually changing the species ...