This is due to the immobile nature of minerals, Eg: Calcium.

(i) Yes. Nitrogen cannot be directly absorbed by plants but they are essential for normal growth and functioning of a plant. Hence they are fixed by bacteria and some fungi.
(ii) It can be utilised only in the form of nitrates (NO₃^-) and nitrites (NO₂^-).

Plants which are growing in nitrogen deficient areas develop insectivorous habit to resolve nitrogen deficiency.
a. Nepenthes (Pitcher plant): Pitcher is a modified leaf and contains digestive enzymes. Rim of the pitcher is provided with nectar glands and acts as an attractive lid. When insect is trapped, proteolytic enzymes will digest the insect.
b. Drosera (Sundew): It consists of long club shaped leaves with tentacles which secrete sticky digestive fluid which looks like a sundew and attracts insects.
c. Utricularia (Bladder wort): Submerged plant in which leaf is modified into a bladder to collect insect in water.
d. Dionaea (Venus fly trap): Leaf of this plant modified into a colourful trap. Two folds of lamina consist of sensitive trigger hairs and when insects touch the hairs it will close and traps the insects.

1. The technique of growing plants in nutrient solution or hydroponics requires purified water and mineral nutrient salts. It is employed in commercial production of vegetables like tomato, seedless cucumber etc.
2. But the nutrient solution must be sufficiently aerated for optimum growth and minerals must be continuously added in the, solution. These activities are not needed for growing plants in the soil.
3. Further the technique is more expensive and may not be feasible to feed a large population.

The process by which nitrate is reduced to ammonia is called nitrate assimilation and occurs during nitrogen cycle.
\({ NO }_{ 3 }^{ - }{ \overset { Nitrate reductase }{ \underset { Mo }{ \longrightarrow } } }{ NO }_{ 2 }^{ - }\)
\({ NO }_{ 2 }^{ - }{ \overset { Nitrate reductase }{ \underset { { Cu }{ Fe } }{ \longrightarrow } } }{ NH }_{ 3 }^{ \\ + }\)

Potassium (K): Maintains turgidity and osmotic potential of the cell, opening and closure of stomata, phloem translocation, stimulate activity of enzymes, anion and cation balance by ion-exchange. It is absorbed as K+ ions.
Deficiency symptoms:Marginal chlorosis, necrosis, low cambial activity, loss of apical dominance, lodging in cereals and curled leaf margin.

Name of the Deficiency Disease and symptoms	Deficiency Minerals
Chlorosis (Yellowing of leaves)	Nitrogen, Potassium, Magnesium, Sulphur, Iron, Manganese,Zinc and Molvbdenum.
Interveinalchlorosis	Magnesium,Iron,Manganese and Zinc
Marginal  chlorosis	Potassium
Necrosis (Death of the tissue)	Magnesium,Potassium,Calcium,Zinc,Molybdenum and Copper.
Stunted growth	Nitrogen,Phosphorus,Calcium,Potassium and Sulphur.
Anthocyanin formation	Nitrogen,Phosphorus,Magnesium and Sulphur
Delayed flowering	Nitrogen,Sulphur and Molvbdenum

1. Utricularia is an insectivorous plant which is also known as bladderwort.
2. It is a aquatic submerged plant in which leaf is modified into a bladder to collect insects in water.

Die back of Citrus, Reclamation disease of cereals and legumes, Chlorosis, Necrosis and Exanthema in Citrus.

Amon and Stout gave criteria required for essential minerals:
1. Elements necessary for growthand development.
2. They should have direct role in the metabolism of the plant.
3. It cannot be replaced by other elements.