1. Nutrition in Plants

Replenishing nutrition of soil

1. Nutrients in the soil keep on declining as plants absorb minerals & nutrients from the soil.
2. Hence, to enrich the soil fertilizers & manures containing nutrients such as nitrogen, potassium, phosphorous, etc. need to be added.
3. This helps in growing healthy plants.

Use of Nitrogen in plants:

1. Carbohydrates are made of carbon, hydrogen & oxygen.
2. Proteins contain nitrogen. 
3. Plants cannot directly absorb the atmospheric nitrogen though present in abundance.
4. The soil has certain bacteria that convert gaseous nitrogen into soluble usable form.
5. This is released in the soil & absorbed by the plants along with water.
6. Plants use this nitrogen to synthesize proteins & vitamins.

Role of Rhizobium

1. Crop plants absorb a lot of nitrogen & the soil becomes deficient in nitrogen.
2. Rhizobium is a soil bacteria that can convert atmospheric nitrogen to usable form.
3. But this bacteria cannot make its own food.
4. It lives in the roots of gram, peas, moong, beans & other legumes,
5. It derives its food from these plants & in return provides them with nitrogen.
6. Thus, it is a symbiotic mode of nutrition.

Use to Farmers:

1. Rhizobium is of great use to farmers.
2. They can reduce the use of nitrogenous fertilizer where leguminous plants are grown.
3. If the soil is deficient of nitrogen, the farmers add nitrogen rich fertilizers to the soil.

In this way the plants fulfil their requirements of nitrogen along with the other constituents. 

To remember:

1. Plants require nitrogen for synthesis of protein.
2. They cannot use the atmospheric nitrogen directly.
3. Rhizobium a soil bacteria helps to convert atmospheric nitrogen in usable form for the plants.