Rhizobium, Azotobacter, blue green algae(cyanobacteria)
Nitrogen fixation is the process by which atmospheric nitrogen is converted into ammonia and different nitrogen oxides. These nitrogenous compounds are used by plants for the synthesis of plant proteins and other compounds.
Ammonia is present in soil, is an important source of nitrogen for plants. Nitrogen promotes plant growth and improves fruit and seed production, resulting in a greater yield. Ammonia is a basic building block for ammonium nitrate fertilizer, which releases nitrogen for the growth of plants. Nitrogen supplied to the plants by ammonia , is a major component of chlorophyll by which plants use sunlight energy to produce glucose from water and carbondioxide.
Plants that are provided with a sufficient amount of soil nitrogen and nitrogen dioxide (NO2) has an increase in the uptake of nutrients, photosynthesis, and nutrient metabolism. Nitrogen oxide (NO) is involved in controlling cell differentiation and lignification, root and shoot development, flowering, growth and reorientation of pollen tubes, senescence and maturation, stomatal movement, plant-pathogen interactions and programmed cell death.