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Class 10 Class 12
Why is there a need for application of fertilisers ?

Fertilisers are chemical compounds used to replenish minerals in crop fields. Three important elements need to be replenished in crop field as they are used up by repeated cultivation of the land. Fertiliser provide these elements like nitrogen, phophorous and potassium . The NPK fertilisers comprise nitrophoshate with potash in varying proportions. The dosage varies according to the crop, soil, season and other climatic conditions. They increase the nutrient content of the soil.

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

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.

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.

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