Mineral Nutrition Short Notes class 11 for neet

Check Mineral Nutrition Notes for NEET 2019 exam! In this article, we are providing short notes on the Topic: Mineral Nutrition which is an important chapter for NEET 2019. This is an important section to pay attention from the Unit Plant Physiology as every year 2-3 questions are asked from this chapter.  In this article, We tried to cover important and brief points for the revision purpose. Moreover, you can download the Mineral Nutrition Notes PDF, we have shared at the end.

MINERAL NUTRITION

Mineral nutrition refers to the process in which minerals or inorganic compounds are absorbed, used and assimilated by plants, thereby synthesizing essential material required for their structure, growth, physiology, and development. These minerals that are being used by the plants in the process are called Mineral Nutrients or Mineral Elements.

 Essential Mineral Elements:

Most nutrients enter the plants from the soil by absorption through roots. In different plants, more than 60 elements are found out of the 105 discovered elements. These can also include gold, selenium, and even radioactive strontium.

The criteria for an element’s essentiality are as follows:

1. It must necessarily support plant growth and reproduction. In its absence, the life cycle of the plants do not complete or their seeds do not set.
2. It must have a specific requirement and none another element can replace it that is, supplying an element does not meet the deficiency of another element.
3. It must have direct participation in plant metabolism.

 On the basis of these criteria, few elements that were found to be essential for the growth and metabolism of the plant are further classified. The basis of this classification was the quantitative requirements of these elements.

1. Macronutrients – The nutrients that are found in large amounts in the plant tissues are macronutrients. These include carbon, oxygen, phosphorus, potassium, magnesium, hydrogen, nitrogen, sulphur, and calcium. Of these, oxygen, hydrogen, and carbon are provided by water and carbon dioxide. On the other hand, other nutrients are absorbed as mineral nutrition from the soil.
2. Micronutrients – The nutrients that are required in trace or small amounts are micronutrients, also known as Trace elements. These include manganese, molybdenum, boron, nickel, iron, copper, zinc, and chlorine.

Besides these 17 essential macros and micronutrients, some beneficial elements (silicon, selenium, sodium, and cobalt) are also there.

Based on their diverse functions, essential elements can also be classified into the following broad categories:

• Structural elements, such as hydrogen, nitrogen, carbon, and oxygen.
• Components of chemical compounds related to energy in plants, such as phosphorus in Adenosine triphosphate (ATP) and magnesium in chlorophyll.
• Inhibitors or activators of enzymes, such as during nitrogen metabolism, molybdenum activates nitrogenase. Also, Zn²⁺ activates alcohol dehydrogenase.
• Having the capability to change a cell’s osmotic potential, such as the role of potassium in closing and opening of stomata.

Role of Macro- and Micronutrients:

Several functions are performed by various macro- and micronutrients. Various functions and forms of these are tabulated below.

• Macronutrients   

MINERAL ELEMENT	FORM AND FUNCTIONS	DEFICIENCY
Nitrogen	1. Plants require nitrogen in the largest amount. 2. The main absorption occurs as NO3-, however, some may also be taken up as NH4+ or NO2-. 3. All plant parts, specifically metabolic active cells, and meristematic tissues, require nitrogen. 4. It is the major component of nucleic acids, hormones, proteins, and vitamins. 5. It is involved in promoting rapid growth with the development of seed and fruit, increasing leaves’ size, and accelerating crop maturity.	Its deficiency leads to a. Reduced lateral breaks. b. Chlorosis. c. Reduced growth.
Phosphorus	1. Its absorption occurs as phosphate ions from the soil. 2. All the phosphorylation reactions involve phosphorus. 3. It is a constituent of certain proteins, nucleotides, cell membranes and all nucleic acids. 4. It allows coenzyme activation for amino acid production, thereby allowing protein synthesis.	Its deficiency leads to a. Delayed maturity. b. Reddish purple margins and tips of leaves. c. Stunted plant growth.
Potassium	1. Buds, root tips, meristematic tissues, and leaves require potassium in large quantities. 2. Its absorption occurs as potassium ions. 3. It maintains the balance between anions and cations in cells and helps in turgidity maintenance of cells, closing and the opening of stomata, enzyme activation, and synthesis of proteins.	Its deficiency leads to a. Stunted growth. b. Brown leaf margins.
Calcium	1. Differentiating and meristematic tissues require calcium. 2. Its absorption occurs as calcium ions. 3. It is used in cell wall synthesis as calcium pectate in middle lamella, during cell division. 4. It is also required for mitotic spindle formation and normal membrane functioning. Its accumulation occurs in older leaves. 5. It regulates metabolic activities by activating certain enzymes.	Its deficiency leads to a. Inhibition of bud growth. b. Weakened leaf growth.
Magnesium	1. Its absorption occurs as divalent magnesium ions. 2. It is associated with activation of photosynthetic and respiratory enzymes, and RNA and DNA synthesis. 3. It is found in chlorophyll and maintains the structure of the ribosome. 4. It helps in seed germination, and in the formation of nuts and fruits.	Its deficiency leads to extensive chlorosis between veins.
Sulphur	1. Its absorption occurs as sulphate. Leaves also take up sulphur is gaseous form as SO2. 2. It is found in several coenzymes, ferredoxin, amino acids (methionine and cysteine), and vitamins (Coenzyme A, biotin, thiamine).	Its deficiency leads to general leaf chlorosis.

• Micronutrients

MINERAL ELEMENT	FORM AND FUNCTIONS	DEFICIENCY
Iron	1. It is obtained as Fe+3 (ferric ions). 2. Compared to micronutrients, plants require iron in the largest amounts. 3. It is found in proteins and is associated with electron transfer, such as cytochromes and ferredoxin, during which it gets reversibly oxidized to form ferrous ions (Fe+2). 4. It helps in the activation of enzyme catalase and in chlorophyll formation.	Its deficiency leads to interveinal chlorosis in the larger amount.
Manganese	1. Its absorption occurs as Mn+2 (manganous ions). 2. It is associated with the metabolism of nitrogen and respiratory and photosynthetic enzyme activation. 3. Its major role is during photosynthesis, where it helps in water splitting to release oxygen.	Its deficiency results in thylakoid membrane disorganization in the chloroplast.
Zinc	1. It is absorbed as zinc ions (Zn+2). 2. It is involved in auxin synthesis and various enzymes’ activation.	Its deficiency leads to interveinal chlorosis and its absence results in rosette-like appearance.
Copper	1. Its absorption occurs as Cu+2 (cupric ions). 2. In plants, it is important for complete metabolism. 3. It plays a role in redox reactions just as iron and can also be reversibly oxidized to form cuprous ions (Cu+3). 4. It is involved in photosynthesis and more than half of it is found in the chloroplast.	Its absence leads to shoot dieback.
Boron	1. Its absorption occurs as B4O72- or BO33-. 2. Its requirement is for the functioning of membranes, elongation of cells, translocation of carbohydrate, uptake and use of calcium ions, germination of pollen, and differentiation of cells.	Its deficiency causes damage to the terminal buds, leading to rosette leaf appearance. It also results in discolouration of tubers, roots and fruits.
Molybdenum	1. Its absorption occurs as MoO22-. 2. It is found in nitrate reductase and nitrogenase enzymes both of which function in the metabolism of nitrogen.	Its absence leads to change in the colour of leaves to pale green along with rolled or cupped margins.
Chlorine	1. Its absorption occurs as chloride ions. 2. It is required for the determination of anion-cation balance and concentration of solutes in cells. It is essential in photosynthesis for splitting of water to release oxygen.	Its absence leads to interveinal chlorosis, non-succulent tissue, and reduced growth.

Deficiency Symptoms of Essential Elements:

• In plants, every mineral element performs one or more specific functional or structural role. The limited supply of these essential elements retards plant growth. This concentration below which the growth of a plant is retarded is called Critical Concentration.
• Below critical concentration, the element is deficient. Certain morphological changes are observed in plants when any element is absent. These changes indicate deficiencies of a certain element called Deficiency Symptoms. These symptoms vary for different elements and deficiency is recovered once the deficient element is provided to the plant.
• Continuous deficiency may lead to plant death. The deficiency symptoms shown by a plant part depends on the element mobility.

• The deficiency symptoms of the elements that are actively mobilised and reach young developing tissues appear in older tissues first. For example, the deficiency symptoms of Magnesium, Potassium, and Nitrogen, are observed in senescent leaves first. The biomolecules that contain these elements gets broken down in the older leaves from where they can be mobilised to the younger leaves.
• However, for relatively immobile elements that do not reach mature organs, the deficiency symptoms are observed in the young tissues first. For example, Calcium and Sulphur, as these elements are a cell’s structural components.

The types of deficiency symptoms are necrosis, premature fall of buds and leaves, inhibition of cell division, and stunted plant growth. These deficiency symptoms are tabulated below.

DEFICIENCY SYMPTOMS	DEFICIENT ELEMENTS
Chlorosis	It refers to chlorophyll loss that results in yellowing of leaves. It is caused due to the deficiency of K, S, Mn, Mo, N, Mg, Fe, and Zn.
Necrosis	It refers to tissue death, specifically leaf tissue. It is caused due to the deficiency of Mg, K, Ca and Cu.
Inhibition of cell division	It is caused due to the low level or lack of K, Mo, N and S.
Delay in flowering	It is caused to the low concentration of Mo, S and N.

       

 Toxicity of Micronutrients:

• The requirement for micronutrients occurs in very less amounts. So, even a moderate decrease in the results in deficiency symptoms. However, even a moderate increase leads to their toxicity. Thus, we can say that there is only a narrow concentration range for these elements that can be considered optimum.
• The concentration due to which the dry weight of tissues is reduced by 10% is toxic.
• Toxicity symptoms cannot be identified easily as the toxicity level is different for various plants. There are various cases when uptake of an element is inhibited due to the excess of another element.

• For example, the toxicity of manganese results in chlorotic veins surrounding the brown spots. Manganese competes with magnesium for enzyme binding, and with the uptake of magnesium and iron. Translocation of calcium in shoot apex is also inhibited by manganese. Thus, Manganese toxicity induces Calcium, Magnesium and Iron deficiency.

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