NEET Biology Important Chapter - Mineral Nutrition

Mineral Nutrition NEET Biology notes are prepared for the students who are looking for last-minute revision notes. This article carries the synopsis of the chapter which can help them in boosting the NEET 2022 preparation. Mineral nutrition in plants is really important from the exam point of view and thus one can keep mineral nutrition NCERT pdf downloaded for getting access to content while being offline. 

Herein we have covered topics such as  Methods to Study the Mineral Requirements of Plants, Essential Mineral Elements, types of nutrients, Mechanism of Absorption of Elements, translocation and other important topics of the chapter. 

Important Topics of Mineral Nutrition

• Essential Mineral Elements

• Mechanism of Absorption of Elements

• Translocation

• Nitrogen Fixation

• Nodule Formation

Important Concepts of the Chapter

The research of the source, mode of intake, distribution, and metabolism of different inorganic substances (minerals) by plants for their growth, development, structure, physiology, and reproduction is known as mineral nutrition.

Methods for Investigating Plant Mineral Requirements

• Hydroponics is a method of growing plants in a nutrient solution without using any soil. This method is used to figure out which nutrients are necessary for plants to grow.

• The plant is cultured in a soil-free, specified mineral solution in this procedure. Purified water and mineral fertilisers are required for these approaches.

• Hydroponics procedures are used to identify essential elements and associated deficiency symptoms. It's also utilised for commercial vegetable cultivation, such as tomato and cucumber.

Essential Mineral Units

Plants contain about 65 distinct elements that are essential mineral nutrients. The following factors are used to judge whether or not an element is necessary.

To complete their life cycle, an element must be absolutely necessary for regular growth and reproduction.

• The element's need must be unique and non-replaceable.

• The element must be directly involved in plant metabolism.

Types of Nutrients

Some Deficiency Symptoms

• The concentration of essential components below which plant growth is slowed is known as the critical concentration.

• Symptoms of deficiency in highly mobile elements (N, P, K, Mg) show first in older plant sections.

• Immobile element (Ca, S) deficiency symptoms develop first in young plant parts because they are not moved from older plant parts.

• Micronutrient toxicity: Micronutrients get toxic when present in higher amounts. Toxic concentration is defined as any tissue concentration that reduces the dry weight of tissue by 10%. Various elements have different critical hazardous concentrations.

Mechanism of Absorption of Elements

• It is split into two halves. 

• Rapid ion intake happens in the open space or outside space of the cells, the apoplast, throughout the first phase. Ions are gently absorbed into the interior space of the cells, the symplast, in the second phase.

• Ion channels and trans-membrane protein allow ions to flow passively in the apoplast. On the other hand, ions enter the symplast by an active process that requires energy expenditure.

• Flux is the term for ion movement. Inflow refers to inner movement, whereas efflux refers to outward movement.

• Translocation of solutes takes place via the help of xylem along with ascending stream of water.

Roles of Various Elements

1. Nitrogen: It is the most abundant element in plants, and it is absorbed by them as $NO_{2}^{-}$, $NO_{3}^{-}$, and $NH_{4}^{+}$. Proteins, nucleic acids, and vitamins all contain it as a primary component.

2. Phosphorus: It is a mineral that plants absorb in the form of phosphate ions from the soil. It is a component of the cell membrane. Phosphorus is required by all nucleic acids and nucleotides.

3. Potassium Ions ($K^{+}$): These are absorbed by the body. Assist in the maintenance of the cation-anion balance in cells. Protein synthesis, as well as the opening and closing of stomata, are all regulated by this mineral.

4. Calcium: Calcium ions ($Ca_{2}^{+}$) are absorbed by plants from the soil. It's used to make cell walls. Certain enzymes are activated by it.

5. Magnesium: $Mg_{2}^{+}$ ions are absorbed by plants. It is mainly involved in activating enzymes which are responsible for respiration, photosynthesis, and DNA and RNA synthesis. It's a component of chlorophyll.

6. Sulphur: Plants get sulphur in the form of sulphate ($SO_{4}^{2-}$). It's found in amino acids (cysteine, methionine), as well as coenzymes and vitamins.

7. Ferric iron: $Fe^{3+}$ is the form of iron that is obtained. It's a crucial component of a protein involved in the transport system.

8. Manganese: It is absorbed as $Mn^{2+}$ ions. During photosynthesis, it plays a crucial role in dividing water to free Hydrogen and Oxygen.

9. Zinc: Zinc is obtained in the form of $Zn^{2+}$ ions. Auxin synthesis necessitates the presence of this amino acid.

10. Copper: It is consumed in the form of cupric ions ($Cu^{2+}$). Utilised in a range of metabolic and redox processes.

11. Boron: It is taken as the ions $BO_{3}^{3-}$ and $B_{4}O_{7}^{2-}$. Calcium uptake, cell elongation, and pollen germination are all dependent on this mineral.

12. Chlorine: It is taken up in the form of $Cl^{-}$ ions. 

Metabolism of Nitrogen

Along with C, H and O, nitrogen is the most abundant element in the living universe. Proteins, nucleic acids, lipids, hormones, and enzymes are all made up of it.

• Nitrogen fixation is the process of converting nitrogen to ammonia. Lightening and UV radiation supply the energy needed to transform atmospheric nitrogen to nitrogen oxide in nature ( $NO$, $NO_{2}$ and $N_{2}O$).

• Nitrogen oxides are produced by industrial combustion, forest fires, cars, and thermal power plants.

• Ammonification is the process of turning organic nitrogen from dead plants and animals into ammonia.

• Ammonia is first converted to nitrite by bacteria such as Nitrosomonas or Nitrococcus, and then to nitrate by bacteria such as Nitrobacter. Nitrification is the name for these processes.

$2 \mathrm{NH}_{3}+3 \mathrm{O}_{2} \xrightarrow[\text{Nitrosomonas}]{\text { Nitrosococcus }} 2 \mathrm{HNO}_{2}+2 \mathrm{H}_{2} \mathrm{O} \\ 2 \mathrm{HNO}_{2}+\mathrm{O}_{2}\xrightarrow[]{\text { Nitrobacter }}2 \mathrm{HNO}_{3}$

• Plants absorb the nitrates and transmit them to the leaves. Denitrification is a process in which bacteria like Pseudomonas and Thiobacillus transform nitrates into free nitrogen. 

$\mathrm{NO}_{3}^{-} \longrightarrow \mathrm{NO}_{2}^{-} \longrightarrow \mathrm{NO} \longrightarrow \mathrm{N}_{2} \uparrow(\text { Molecular form) }$

Biological nitrogen fixation is the conversion of nitrogen to ammonia by living organisms. Nitrogen fixer is a prokaryotic bacterium that contains the enzyme nitrogenase.

• Nitrogen-fixing microorganisms can be either symbiotic (Rhizobium) or free-living (Bacillus niger).

• The legume-bacteria interaction, in which rod-shaped Rhizobium thrives in a symbiotic relationship with nodules of leguminous plants, is an example of symbiotic biological nitrogen fixation.

• Due to the presence of leguminous haemoglobin or leg-haemoglobin, the central area of the nodule is pink or red.

Development of a Root Nodule

Nodulation Process

1. Rhizobium and root chemical recognition

2. Curling of the root hairs

3. Infection strand formation

4. Rhizobia invasion of the roots 

5. Formation of nodule tissue

6. Bacteria transform into bacteroids, which produce the nitrogenase enzyme.

7. Legume is a source of carbon for Rhizobia. Rhizobia gives fixed nitrogen to the legume.

Mechanism of Biological Fixation of Nitrogen

• Nitrogenase is an anaerobic enzyme that is super vulnerable to molecular oxygen. Leg-haemoglobin, an oxygen scavenger, is found in the nodules to safeguard this enzyme from oxygen.

• Each $NH_{3}$ generated by the nitrogenase enzyme requires a significant amount of energy (18 ATP).

$\mathrm{N}_{2}+16 \mathrm{ATP}+8 \mathrm{H}^{+}+8 \mathrm{e}^{-} \longrightarrow 2 \mathrm{NH}_{3}+16 \mathrm{ADP}+16 \mathrm{Pi}+\mathrm{H}_{2}$

The first products of nitrogen absorption are amino acids. Plants can assimilate both nitrate and ammonium ions ($NH_{4}^{+}$) in most cases. In plants, $NH_{4}$ is used to synthesise amino acids. The following are the two processes for amino acid synthesis:

• Reductive Ammonia: Ammonia interacts with Ketoglutaric acid to create glutaric acid in a reductive amination reaction.

$\alpha-ketogltuamate + NH_{4}^{+} + NADPH \xrightarrow[dehydrogenase]{glutamate}Glutamate + NADP + H_{2}O$

• Transamination: The transfer of amino groups from amino acids to the keto group of a keto acid is known as transamination. Transamination produces other amino acids from glutamic acid, which is the major amino acid from which $NH_{3}$ is transferred. All of these processes are catalysed by the enzyme transaminase.

$\text { amino acid } 1+\alpha \text { - Keto acid } 2 \rightarrow \alpha \text {-Keto acid } 1+\text { amino acid } 2$

Asparagine and glutamine are two major amides present in plants as structural components of proteins. They are created by adding another amino group to aspartic acid and glutamic acid.

Solved Examples from Chapter

1. ‘Whip-tail’ disease in cauliflower is noted due to deficiency of

1. Manganese

2. magnesium

3. Molybdenum

4. Nitrogen

Ans: c. Molybdenum

Due to a lack of molybdenum, cauliflower develops 'Whip-tail' illness. Cauliflower is the most vulnerable crop to a lack of molybdenum ($Mo$). Under conditions of high fertility, light sandy soils with pH levels close to or below pH 6 can reveal significant micronutrient shortage, which becomes less available as the soil Mo deficiency progresses. The sole plant necessary acidifier is molybdenum, which is the polar opposite of copper, zinc, and iron.

Key point to remember- Cauliflower is the most vulnerable crop to a lack of molybdenum ($Mo$).

2. Choose the correct option

1. Amides are transported forms of nitrogen as they have more nitrogen

2. Legumes of tropical origin (e.g., soybean) transport ureides

3. The host produces globin part and bacterial symbiont produces haem part of leghemoglobin ($N_{2}$ fixing pigment)

4. All of the above.

Ans: d. All of the above

Amides have more nitrogen than amino acids and are transferred through xylem vessels to different sections of the plant. Tropical legumes (such as soya bean) transport ureides.

In addition, the nitrogen to carbon ratio of these molecules is unusually high.

Leghemoglobin ($N_{2}$ fixing pigment) is made up of two parts: globin produced by the host (plant) and haem produced by the bacterial symbiont.

3. Identify the A to D correctly in the given diagram of root nodule development and choose the correct option accordingly.

1. A-Rhizobium bacteria, B-cortex cell, C-Outer cortex, D-Infection thread

2. A-Rhizobium bacteria, B-Root hair, C-Inner cortex, D-Infection thread

3. A-Rhizobium bacteria, B-Endodermal cell, C-Inner endodermis D-Infection thread

4. A-Nitrosomonas bacteria, B-Root hair, C-Inner cortex, D-Infection thread

Ans: b. A-Rhizobium bacteria, B-Root hair, C-Inner cortex, D-Infection thread

Key point to remember- Below given diagram is to be considered well to answer this question.

Solved Problems of Previous Years’ Questions from Chapter

1. The product(s) of reaction catalysed by nitrogenase in root nodules of a leguminous plant is/are.

1. Ammonia and oxygen

2. Ammonia and hydrogen

3. Ammonia alone

4. Nitrate alone

Ans: The reduction of $N_{2}$ to ammonia is carried out by the nitrogenase enzyme. Ammonia and hydrogen are the products of the nitrogenase-catalysed process in the root nodules of leguminous plants.

Key point to remember: Nodules act as the site for $N_{2}$ fixation.

2. Match the following concerning essential elements and their functions in plants:

Select the correct option:

1. (a) – iii; (b) – iv; (c) – ii; (d) – i

2. (a) – iv; (b) – i; (c) – ii; (d) – iii

3. (a) – ii; (b) – i; (c) – iv; (d) – iii

4. (a) – iv; (b) – iii; (c) – ii; (d) – i

Ans: a. (a) – iii; (b) – iv; (c) – ii; (d) – i

3. Thiobacillus is a group of bacteria helpful in carrying out:

1. Chemoautotrophic fixation

2. Nitrification

3. Denitrification

4. Nitrogen fixation

Ans: c. Denitrification

Denitrification, or the conversion of nitrogen oxides to free $N_{2}$, is caused by Thiobacillus denitrificans.

Key point to remember: Denitrification is carried out in four steps:

$\mathrm{NO}_{3}^{-} \longrightarrow \mathrm{NO}_{2}^{-} \longrightarrow \mathrm{NO} \longrightarrow \mathrm{N}_{2} \uparrow(\text { Molecular form) }$

Practice Questions

1. The limiting factor in nitrogen fixation of soil is 

1. Soil nature (pH)

2. Light

3. Temperature

4. Air

2. If by radiation all nitrogenase enzyme is inactivated, then there will be no

1. Fixation of nitrogen in legumes

2. Fixation of atmospheric nitrogen

3. Conversion from nitrate to nitrite in legumes

4. Conversion from ammonium to nitrate in the soil

3. In plants, flowering is delayed due to the deficiency of

1. Mo, S and N

2. Mo, S, N and K

3. Ca, Mg, Cu and K

4. Mg, Zn, Mn and K

1. Ans: a. soil nature (pH)

The excessive pH of the soil has an effect on nodulation by limiting Rhizobia colonisation of the soil and legume rhizosphere. Low quantities of phosphorus, calcium, and molybdenum, as well as high levels of hazardous elements, are common in highly acidic soils, whereas sodium chloride, bicarbonate, and borate are common in highly alkaline soils (pH>8.0).

2. Ans: a. fixation of nitrogen in legumes

Nitrogenase is a protein that aids in the catalysis of the conversion of atmospheric $N_{2}$ to $NH_{3}$. There will be no nitrogen fixing in legumes if this enzyme is inactive.

3. Ans: a. Mo, S and N

Because of a lack of Mo, S, and N in plants, flowering is delayed.

Nitrogen- An excess of nitrogen can cause blooming to be delayed, while a lack can diminish output.

Molybdenum- This mineral is part of the enzyme that converts nitrates to ammonia.

Sulphur- It is a structural component that is essential for chlorophyll synthesis.

Conclusion

The synopsis of the chapter Mineral Nutrition includes all the major topics as per the NEET Examination and at the end of the article, mineral nutrition neet questions, sample questions have been added which can help the student in understanding the kind of pattern that the NEET 2022 examination has. Moreover, there are practice questions added that a student can try in order to rate the learning.