Introduction:
Nitrogen is one of the essential nutrients that is required by plants for their growth and development. It is a vital component of protein and chlorophyll, which is responsible for the production of energy and photosynthesis in plants. Nitrogen is present in the soil in various forms, and plants absorb it mainly in the form of certain compounds.

Forms of Nitrogen in Soil:
Nitrogen is present in the soil in various forms, including:

1. Organic Nitrogen - It is present in the form of dead plant and animal material and is not available to plants directly.
2. Inorganic Nitrogen - It is present in the form of nitrate (NO3-), ammonium (NH4+), and nitrite (NO2-) ions, which are available to plants.

How Plants Absorb Nitrogen:
Plants absorb nitrogen mainly in the form of nitrate ions (NO3-), which is the most easily available form of nitrogen in the soil. Nitrate ions are negatively charged and are attracted to the positively charged roots of the plants. The process of absorption of nitrogen by plants involves the following steps:

1. Nitrate ions present in the soil get dissolved in the water present in the soil.
2. The roots of the plants absorb the nitrate ions along with the water through the process of diffusion.
3. The nitrate ions then move through the root cells and enter the xylem vessels, which transport water and minerals to the rest of the plant.
4. Nitrate ions are used by the plant for the synthesis of amino acids, which are the building blocks of proteins.

Conclusion:
Nitrogen is an essential nutrient that is required by plants for their growth and development. Plants absorb nitrogen mainly in the form of nitrate ions, which are available in the soil. The process of absorption of nitrogen by plants involves the steps of diffusion and transportation through the xylem vessels.