As we know, all living beings need energy for survival. Have you ever thought about how a plant receives the energy for its growth and development? Several elements encourage growth and development in plants. The elements which the plants require to complete their life cycle are known as essential elements of plants.

Plants absorb most of the essential elements from the soil. Each element has a specific role in the plant’s growth, which any other element cannot replace. In this article, we will provide detailed information on Essential elements of plants. Continue reading to learn more about the essential elements of plants!

What are Essential Elements in Plants?

These elements have a specific structural or physiological role. These are indispensable for plants to complete their life cycle. There are six biologically essential elements: C, H, O, N, P, S, without which no cellular components can be formed. More than 60 elements out of nearly 105 known ones are found in plants. Plants require 17 essential elements for growth but there are some beneficial elements such as sodium, silicon, cobalt and selenium required by higher plants.

Fig: Essential Elements of Plants

Criteria of Essentiality of Elements of Plants

An essential element has the following criteria:
1. The element is necessary for the plant for supporting the normal growth and reproduction of the plant. In the absence of such elements, the normal growth and metabolism of the plant will be affected.
2. The element is directly or indirectly involved in the metabolism of the plant.
3. The element is the structural and functional molecule.
4. The absence of that given element can cause specific symptoms of deficiency.
5. Some other elements cannot compensate for the deficiency symptom caused by the deficiency of one element.

Classification of Essential Elements of Plants

Below we have provided the classifications of essential elements of plants:

1) Based on the quantity required for the plants, there are two types of elements
a. Macronutrients are needed in more than or equal to 10 mMol per Kg of body weight. Sodium, Potassium, Sulphur, Magnesium, Nitrogen, Calcium are macronutrients.
b. Micronutrients are needed less than 10 mMol per Kg of body weight. Boron, Copper, Molybdenum, Ferrous, Zinc, Chlorine, Nickel, Manganese are micronutrients.

Fig: Macronutrients and Micronutrients

2) Based on functions performed by the element in the plant body
a. Structural elements are significant components of biomolecules. Carbon, Oxygen, Hydrogen, etc., are in this category. Nitrogen is also in this category, as it is a major part of the protein.
b. Enzyme activators are metallic or non-metallic cofactor elements.
I. Mo – Nitrogenase, Nitrate reductase enzymes
II. Zn – Alcohol dehydrogenase enzyme
III. Cu – Cytochrome, Plastocyanin
IV. Fe – Ferredoxin, Cytochrome, Plastoquinone
V. Mg – Hexokinase, RuBisCO, PEPCO, Pyruvate kinase
VI. Mn – Photolysis of water
VII. Cl – Photolysis of water
c. Osmotic potential maintainer elements balance the osmotic concentration of the cell. Potassium and chlorine are in this category.
d. Energy-related elements are part of high energy molecules and are needed for the metabolism of every cell. Phosphorus (in ATP, GTP, etc.), nitrogen (in NADP, NAD, FAD, etc.) are examples of this category.

Role of Essential Elements and their Deficiency Symptoms of Plants

Below we have provided the role of essential elements and their deficiency symptoms of plants:

1. Macronutrients
a. They are needed in more quantities (often more than 10 mMol per Kg body weight).
b. The concentration below which the plants start showing restricted growth and other symptoms is called critical concentration.
c. If the element is:
i. Actively mobilised, then the same is taken from the older part and given to young tips and growing parts. Thus, deficiency symptoms are prominent in older tissue first like Na, K, Mg, etc.
ii. Not-actively mobilised, then the same is retained more in older tissues, and less is made available for younger tissues. The deficiency symptoms are prominent in younger tissue first. Like, Ca, S, etc.

Element	Source and Form of Absorption	Physiological Roles	Deficiency Symptoms
1. Nitrogen	Soil. Nitrate (NO3–), Nitrite (NO2–), Ammonia (NH4+)	a) Nitrogen is a component of proteins, DNA, RNA, ATP, GTP, vitamins, hormones, etc. b) Nitrogen plays a role in every metabolic activity.	a) Chlorosis (yellowing and dechlorophyllisation) b) Inhibition of cell division. c) Stunted growth. d) Delay in flowering. e) Symptoms appear in senesced leaves (as it is an actively mobile element).
2. Phosphorous	Soil. PO4 –, PO3 –	a) It is a component of ATP, GTP, DNA, RNA, NADP, etc.	a) Chlorosis. b) Necrosis anthocyanin formation. c) Purple or red spot in leaves. d) Delay in seed germination. e) Protein synthesis decreased. f) Premature leaf fall.
3. Sulphur	Soil. SO3 -2	a) Sulphur is a Component of methionine, cysteine amino acids, thiamine, vitamins, Ferredoxin and Co-A.	a) Development of more anthocyanin pigment. Chlorosis in younger leaves. b) Stunted growth. c) Delay in flowering. e) Cell division reduced.
4. Calcium	Soil. Ca+2	a) Calcium is a component of middle lamellae (Ca-pectate salts). b) It is required for spindle fibre formation by condensation of α-tubulin protein. c) It is needed for cell division and ATPase, α- amylase enzymes. d) It helps in maintaining chromosome structures.	a) The disintegration of the growing apex. b) Chlorosis on margins of younger leaves. c) Necrosis. d) Stunted growth.
5. Magnesium	Soil. Mg+2	a) Magnesium is needed for chlorophyll formation, photolysis of water to maintain the integrity of ribosomes and protein synthesis. b) It is a component of middle lamella (Mg-pectate salt). c) It is an activator of photosynthetic and respiratory enzymes.	a) Necrosis. b) Chlorosis. c) Stunted growth. d) Improper synthesis of protein. e) The leaf tissue between the veins may be yellowish, bronze, or reddish, while the leaf veins remain green.
6. Potassium	Soil. K+	a) Potassium maintains osmotic balance in cells and anion-cation balance in the cells. b) It is needed for stomatal opening and closing and synthesis of chlorophyll. c) It is involved in protein synthesis.	a) Chlorosis. b) Necrosis. c) Plastid disintegration. d) Loss of cambial activity. e) Scorched leaf tip. f) Root curling.

2. Micronutrients
a. They are needed in less than 10 mMol per Kg of body weight.
b. Micronutrients are needed in low quantities.

Element	Source and form of absorption	Physiological roles	Deficiency symptoms
Boron	Soil. As BO33-, B4O7–	a) Boron is needed for pollen tube germination on stigma, phloem loading during translocation and uptake and utilisation of Ca+2 ions. b) It is essential for cell differentiation.	a) Loss of apical dominance. b) Absence of root nodules in legumes. c) Delay and inhibit seed germination. d) Death of shoot and root tips takes place. e) The growth of the root stopped.
Molybdenum	Soil. MoO42-	a) It is needed for nitrate reductase and nitrogenase enzymes. b) It is more required in root elongation and development.	a) Affect nitrogen fixation. b) It inhibits flowering. c) Whiptail disease of leaves occurs.
Zinc	Soil. Zn+2	a) It is needed for the synthesis of auxins. b) It is an activator for many enzymes, including alcohol dehydrogenase.	a) Shortening of internodes and deformation of leaves takes place. b) It inhibits the formation of seeds.
Iron	Soil Fe+2, Fe+3	a) Components of Ferredoxin, cytochrome, etc. b) Essential for chlorophyll and pigment synthesis. c) Activator for many enzymes.	a) Disintegration of a chloroplast. b) Immature leaf fall. c) Rapid interveinal chlorosis occurs.
Chlorine	Soil. Cl–	a) Chlorine is used to maintain osmotic balance, anion-cation balance, solute concentration like Na and K. b) It is needed for the photolysis of water.	a) Stunted growth. b) Less rooting and shoot formation. c) Bronze colour in leaves.
Nickel	Soil. Ni+2	a) Component of urease and hydrogenase enzymes. b) It is involved in the metabolism of urea.	a) Delay in seed germination. b) Growth reduced. c) Reduced fruiting.
Copper	Soil. Cu+2	a) Copper is needed for pigments, plastocyanin protein of ETS.  b) It is essential for respiration and photosynthesis.	a) The fall of immature leaves and buds. b) Stunted growth. c) Necrosis of tip in young leaves
Manganese	Soil. Mn+2	a) Manganese is needed for photolysis.	a) Chlorotic and necrotic spots on leaves. b) Chlorosis in young and older leaves. c) Late flowering.

Fig: Different Deficiency Symptoms of Elements in Plants

Difference Between Macronutrients and Micronutrients

The difference between macronutrients and micronutrients are as follows:

Macronutrients	Micronutrients
1. These nutrients are required in large quantities.	1. These nutrients are required in small quantities.
2. These are used for the building of body structures.	2. These do not have any role in building body structures.
3. These are usually not toxic to the cell, even if they are present in relatively higher concentrations.	3. These are toxic to the plants if they are present in excess in the cell.
4. Some of the macronutrients help to maintain the osmotic potential of the cells.	4. They do not have any role in maintaining the osmotic potential of the cells.
5. The majority of the macronutrients are absorbed through roots; some like C, H and O are not absorbed through roots.	5. All the micronutrients are absorbed through roots.
6. Majority of macronutrients are minerals, some like C, H and O are non-minerals.	6. All micronutrients are minerals.
7. Examples: Carbon, hydrogen, oxygen, sulphur, potassium, calcium, magnesium and phosphorus.	7. Examples: Boron, molybdenum, manganese, copper, zinc, nickel, chlorine and iron.

Toxicity of Minerals

The toxicity of minerals are as follows:

1. Any mineral element or ion concentration in the tissue that can cause the dry weight of that tissue by 10% is called toxic concentration.
2. The moderate increase in their absorption by plants may cause toxicity.
3. The toxicity of one mineral mostly leads to the inhibition of absorption of other micronutrients.
4. Mn toxicity: 
a. It reduces the uptake of Fe and Mg.
b. It prevents the binding of Mg with enzymes.
c. It inhibits the translocation of Ca shoot apices.
Therefore, excess of Mn causes deficiency of Fe, Mg, Ca.

Summary

Plants absorb certain essential elements from the soil required for the plant’s growth and development. These essential elements based on essentiality are of two types macronutrients and micronutrients. The six macronutrients are nitrogen, sulphur, phosphorus, calcium, magnesium and potassium. The micronutrients are boron, molybdenum, zinc, iron, chlorine, nickel, copper and manganese. All elements play a significant role that helps the plant to complete its lifecycle from the beginning of germination to flowering.

FAQs on Essential Elements in Plants

Q.1. What are essential elements?
Ans: These elements have specific structural or physiological roles. These are required for plants to complete their life cycle—examples: Carbon, hydrogen, oxygen, nitrogen, phosphorus and sulphur.

Q.2. What are the six most important elements?
Ans: The six most important elements are C, H, O, N, P and S.

Q.3. What are non-essential elements?
Ans: These elements are required in some plants but not all. Their absence does not produce any major deficiency symptoms in plants—examples: cobalt, silicon, boron, molybdenum, etc.

Q.4. Write down the role of potassium in plants?
Ans: a. Potassium maintains osmotic balance in cells and anion-cation balance in the cells.
b. It is needed for stomatal opening and closing and synthesis of chlorophyll.

Q.5. Write the deficiency symptoms of magnesium?
Ans: The deficiency symptoms of magnesium are necrosis, chlorosis, stunted growth, and improper synthesis of protein.

NCERT Solutions for 11th Biology

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