Question

what is ntrogen cycle and nitrogen fixation and rhizobium bacteria

Answer 1

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1) Nitrogen cycle, circulation of nitrogen in various forms through nature. Nitrogen, a component of proteins and nucleic acids, is essential to life on Earth. Although 78 percent by volume of the atmosphere is nitrogen gas, this abundant reservoir exists in a form unusable by most organisms. Through a series of microbial transformations, however, nitrogen is made available to plants, which in turn ultimately sustain all animal life. The steps, which are not altogether sequential, fall into the following classifications: nitrogen fixation, nitrogen assimilation, ammonification, nitrification, and denitrification.

2) Nitrogen fixation, in which nitrogen gas is converted into inorganic nitrogen compounds, is mostly (90 percent) accomplished by certain bacteria and blue-green algae. A much smaller amount of free nitrogen is fixed by abiotic means (e.g., lightning, ultraviolet radiation, electrical equipment) and by conversion to ammonia through the Haber-Bosch process.

3) Rhizobium is a bacterium ( sing. Of bacteria) which can convert atmospheric nitrogen into usable form for plants . It cannot make its own food . So, it often lives in the root of some lugumes and provides them with nitrogen. In return, the plants provide food and shelter to the bacterium. They, does symbiotic relationship. This association is helpful to farmers as these bacteria can reduce the use of nitrogenous fertilisers where leguminous plants are grown.

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Answer 2

Answer:

Two kinds of nitrogen-fixing bacteria are recognized. The first kind, the free-living (nonsymbiotic) bacteria, includes the cyanobacteria (or blue-green algae) Anabaena and Nostoc and genera such as Azotobacter, Beijerinckia, and Clostridium. The second kind comprises the mutualistic (symbiotic) bacteria; examples include Rhizobium, associated with leguminous plants (e.g., various members of the pea family); Frankia, associated with certain dicotyledonous species (actinorhizal plants); and certain Azospirillum species, associated with cereal grasses.

Explanation: