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Class 10 Class 12
Explain with examples :
(1) Macronutrients,
(2) Micronutrients,
(3) Toxic elements ,
(4) Essential elements.

(a) Macronutrients :

(i) Macronutrients are generally present in plant tissues in large amounts in excess of 10m mole kg–1 of dry matter. For example - Carbon, hydrogen, nitogen, phosphorous, and oxygen

(b) Micronutrients : Micronutrients or trace elements are needed in less than 10mmole kg–1  of dry matter eg. iron, manganese, copper, molybdenum, zinc, boron, chlorine and nickel.

(c) Toxic elements : Any mineral ion or element which reduces dry weight by 10% of plant is called toxic element. Toxicity of element differs from plant to plant. The elements when present in large amounts much more than what is needed becomes toxic.

(d) Essential elements : These are the elements which are essential for the growth of the plants. The plant cannot complete their lifecycle in the absence of it.  They are C, H, O, N, P, S, K, Ca, Mg, Fe, Mn, Cu, Mo, Zn, B, CI and NL

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.

Name the best known symbiotic nitrogen fixing bacterium.

Rhizobium.

Which pigment is present in the root nodules of legumes ?

Leghaemoglobin.

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

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

Anaerobic.

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