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Class 10 Class 12
Describe the natural method of nitrogen fixation.

Natural method of nitrogen fixation : When lightening occurs, atmospheric nitrogen and oxygen combine to form NO. The nitric oxide [NO] combines with oxygen to from NO2. This nitrogen dioxide combines with rain water to form HNO (Hyponitrous acid) and HNO2 or HNO2 and HNO3. These nitrous acids and nitric acid are washed into the soil along with rain water and cause Acid Rain. This acidic rain water combines with other mineral salts to form nitrities and nitrates. The nitrites and nitrates are absorbed by the plants.

Name the best known symbiotic nitrogen fixing bacterium.

Rhizobium.

What is Hidden hunger in the case of plants?

Hidden hunger refers to a situation in which a crop needs more of a given nutrient yet has shown no deficiency symptoms. The nutrient content is above the deficiency symptom zone but still considerably needed for optimum crop production

How is nitrogenase enzyme protected ?

The nitrogenase enzyme is very sensitive to the molecular oxygen. It requires anaerobic conditions to work. The leg-haemoglobin in the nodule acts as an oxygen scavenger just meainting the anaerobic condition needed by the enzyme.

Which pigment is present in the root nodules of legumes ?

Leghaemoglobin.

What type of condition is created by leghaemoglobin in the root modules of legumes ?

Anaerobic.

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