ESSENTIAL MINERAL ELEMENTS Questions in English

(C) Essential elements are classified based on their functions. Elements that act as components of biomolecules and are structural elements of cells are primarily $C$,$H$,$O$,and $N$.
These four elements form the backbone of all organic molecules such as carbohydrates,proteins,lipids,and nucleic acids,which constitute the structural framework of the cell.
Therefore,the correct group is $Carbon$,$Hydrogen$,$Oxygen$,and $Nitrogen$.

(B) In addition to the $17$ essential elements,there are some beneficial elements such as sodium $(Na)$,silicon $(Si)$,cobalt $(Co)$,and selenium $(Se)$.
These elements are required by higher plants for specific physiological functions but are not considered strictly essential for all plants.
Therefore,the correct option is $B$.

(C) The essential nutrient required by plants in the greatest amount is Nitrogen $(N)$.
Nitrogen is a major constituent of proteins,nucleic acids,vitamins,and hormones.
Phosphorylation reactions typically involve Phosphorus $(P)$.
Synthesis of auxin is associated with Zinc $(Zn)$.
Splitting of water during photosynthesis is associated with Manganese $(Mn)$ and Chlorine $(Cl)$.

(B) The dry weight of a plant is the weight of the plant after all the water has been removed.
Plants obtain carbon,hydrogen,and oxygen primarily from the atmosphere $(CO_2)$ and water $(H_2O)$.
These three elements constitute the vast majority of the organic biomass of the plant,forming the structural components like cellulose,hemicellulose,and lignin.
Therefore,carbon,hydrogen,and oxygen make up the major part of the dry weight of plants.

(A) The elemental analysis of plant tissues reveals that carbon $(C)$,hydrogen $(H)$,and oxygen $(O)$ are the most abundant elements found in plants. Among these,carbon is the primary structural component of all organic molecules,including carbohydrates,proteins,lipids,and nucleic acids,which constitute the bulk of the plant's dry weight. Therefore,carbon is present in the highest amount compared to other elements like nitrogen,manganese,or iron.

(C) Essential mineral elements for plants are those that are absolutely necessary for supporting normal growth and reproduction.
Criteria for essentiality include:
$1$. The plant cannot complete its life cycle without the element.
$2$. The element is directly involved in the metabolism of the plant.
$3$. The requirement of the element is specific and not replaceable by another element.
Potassium $(K)$,Iron $(Fe)$,and Zinc $(Zn)$ are well-established essential micronutrients or macronutrients.
Iodine $(I)$ is not considered an essential mineral element for higher plants,although it may be found in some marine algae.

(A) The dry weight of plants is primarily composed of organic compounds such as carbohydrates,proteins,lipids,and nucleic acids.
These organic molecules are essentially built from carbon,hydrogen,and oxygen atoms.
Carbon is obtained from atmospheric $CO_2$,while hydrogen and oxygen are derived from water $(H_2O)$.
Therefore,carbon,hydrogen,and oxygen constitute the major portion of the dry matter in plants.

(C) Essential elements are classified into two categories based on their quantitative requirements: macronutrients and micronutrients.
Macronutrients are required in large amounts (generally $10 \text{ mmol kg}^{-1}$ of dry matter).
These include Carbon,Hydrogen,Oxygen,Nitrogen,Phosphorus,Sulphur,Potassium,Calcium,and Magnesium.
Micronutrients are required in small amounts (less than $10 \text{ mmol kg}^{-1}$ of dry matter).
These include Iron,Manganese,Copper,Molybdenum,Zinc,Boron,Chlorine,and Nickel.
Among the given options,$Ca$ (Calcium) is a macronutrient,while $Zn$,$Cu$,and $Mn$ are micronutrients.

(N/A) Plants absorb a wide variety of elements from the soil through their root systems. However,an element is considered 'essential' only if it is directly involved in the plant's metabolism,growth,and reproduction.
Many elements are absorbed by plants simply because they are present in the soil solution,even if they serve no biological function. For example,plants growing near radioactive sites often accumulate radioactive isotopes,and plants near mining areas may accumulate heavy metals like gold or selenium.
These elements are present in the plant tissues,but they are not required for the plant's life cycle. Therefore,the presence of an element in a plant does not automatically imply that it is essential for its survival.

(N/A) Macronutrients: These are nutrients required by plants in large amounts. They are present in plant tissues in concentrations greater than $10 \, mmol \, kg^{-1}$ of dry matter. Examples include $C, H, O, N, P, K, S, Ca,$ and $Mg$.
Micronutrients: Also known as trace elements,these are present in plant tissues in very small amounts,i.e.,concentrations less than $10 \, mmol \, kg^{-1}$ of dry matter. Examples include $Fe, Mn, Cu, Mo, Zn, B, Cl,$ and $Ni$.
Beneficial nutrients: These are elements that are not strictly essential but are beneficial for the growth of higher plants. Examples include $Na, Si, Co,$ and $Se$.
Toxic elements: Any mineral ion concentration in tissues that reduces the dry weight of tissues by about $10\%$ is considered toxic. For example,excess $Mn$ competes with $Fe$ and $Mg$ for uptake and inhibits $Ca$ translocation to shoot apices,causing deficiency symptoms of $Fe, Mg,$ and $Ca$.
Essential elements: These are elements that are absolutely necessary for plant growth,metabolism,and reproduction. Their requirement is specific and non-replaceable. They are further classified into macronutrients and micronutrients.

(N/A) $\Rightarrow$ Most minerals present in the soil can enter plants through their roots. In fact,more than $60$ of the $105$ elements discovered so far are found in different plants.
$\Rightarrow$ Some plant species accumulate selenium,while others store gold.
$\Rightarrow$ Plants growing near nuclear test sites can take up radioactive strontium.
$\Rightarrow$ Modern techniques can detect minerals even at very low concentrations,such as $10^{-8} \text{ g/mL}$.
$\Rightarrow$ The criteria for the essentiality of an element are as follows:
$(a)$ The element must be absolutely necessary for supporting normal growth and reproduction. In the absence of the element,plants cannot complete their life cycle or set seeds.
$(b)$ The requirement of the element must be specific and not replaceable by another element. In other words,the deficiency of one element cannot be met by supplying another element.
$(c)$ The element must be directly involved in the metabolism of the plant.
$\Rightarrow$ Based on these criteria,only a few elements have been found to be absolutely essential for plant growth and metabolism.

(N/A) Mineral elements are classified into two main types based on the quantity required by plants:
$(i)$ Macronutrients: These are generally present in plant tissues in large amounts (in excess of $10 \text{ mmol } kg^{-1}$ of dry matter).
$\Rightarrow$ The macronutrients include carbon,hydrogen,oxygen,nitrogen,phosphorus,sulphur,potassium,calcium,and magnesium.
$\Rightarrow$ Of these,carbon,hydrogen,and oxygen are mainly obtained from $CO_2$ and $H_2O$,while the others are absorbed from the soil as mineral nutrition.
$(ii)$ Micronutrients (Trace elements): These are needed in very small amounts (less than $10 \text{ mmol } kg^{-1}$ of dry matter).
$\Rightarrow$ These include iron,manganese,copper,molybdenum,zinc,boron,chlorine,and nickel.
$\Rightarrow$ In addition to the $17$ essential elements named above,there are some beneficial elements such as sodium,silicon,cobalt,and selenium,which are required by higher plants.

(N/A) Essential elements can be grouped into four broad categories based on their diverse functions:
$(A)$ Essential elements as components of biomolecules and hence structural elements of cells,e.g.,carbon,hydrogen,oxygen,and nitrogen.
$(B)$ Essential elements that are components of energy-related chemical compounds in plants,e.g.,magnesium in chlorophyll and phosphorus in $ATP$.
$(C)$ Essential elements that activate or inhibit enzymes. For example,$Mg^{2+}$ is an activator for both ribulose bisphosphate carboxylase-oxygenase $(RuBisCO)$ and phosphoenol pyruvate carboxylase ($PEP$ carboxylase). $Zn^{2+}$ activates alcohol dehydrogenase. $Mo$ activates nitrogenase during nitrogen metabolism.
$(D)$ Essential elements that can alter the osmotic potential of a cell,such as potassium $(K^+)$,which plays an important role in the opening and closing of stomata.

(D) $\Rightarrow$ The criteria for the essentiality of an element are as follows:
$(a)$ The element must be absolutely necessary for supporting normal growth and reproduction. In the absence of the element,the plants cannot complete their life cycle or set seeds.
$(b)$ The requirement of the element must be specific and not replaceable by another element. In other words,the deficiency of any one element cannot be met by supplying another element.
$(c)$ The element must be directly involved in the metabolism of the plant.

(D) Essential minerals are crucial for plant growth and development for several reasons:
$1$. Structural components: Minerals like calcium are essential for the formation of cell walls (calcium pectate).
$2$. Osmotic regulation: Minerals like potassium play a vital role in maintaining the osmotic potential of cells,which is essential for turgor pressure and stomatal movement.
$3$. Enzymatic activity: Many minerals act as cofactors or activators for various enzymes. For example,magnesium is a cofactor for enzymes involved in photosynthesis and respiration.
$4$. Energy transfer: Minerals like phosphorus are integral components of $ATP$,which is the energy currency of the cell.
Therefore,all the listed functions are important roles of essential minerals.

(N/A) Nitrogen $(N)$ is one of the most essential mineral elements required by plants and other organisms. Its importance includes:
$1$. It is a major constituent of proteins,which are the building blocks of life.
$2$. It is an essential component of nucleic acids ($DNA$ and $RNA$),which carry genetic information.
$3$. It is a key element in vitamins and many hormones.
$4$. It is a structural component of chlorophyll,the pigment responsible for photosynthesis in plants.
$5$. It is present in coenzymes like $NAD$,$NADP$,and $ATP$,which are vital for metabolic reactions.

(N/A) $(1)$ Mineral nutrition is the study of the absorption,distribution,and metabolism of mineral elements by plants.
$(2)$ Essential mineral elements are those elements that are absolutely necessary for supporting the normal growth and reproduction of plants. In the absence of these elements,plants cannot complete their life cycle or set seeds.

(N/A) Essential elements are those chemical elements that are absolutely necessary for the growth, development, and completion of the life cycle of a plant.
The criteria for essentiality, as proposed by Arnon and Stout $(1939)$, are:
$1$. The plant must be unable to complete its vegetative or reproductive stage in the absence of the element.
$2$. The requirement of the element must be specific and not replaceable by another element.
$3$. The element must be directly involved in the metabolism of the plant.
Based on the quantity required, minerals are classified into two categories:
$1$. Macronutrients: These are present in plant tissues in large amounts (generally in excess of $10 \text{ mmol kg}^{-1}$ of dry matter). Examples include $C, H, O, N, P, S, K, Ca,$ and $Mg$.
$2$. Micronutrients: These are needed in very small amounts (less than $10 \text{ mmol kg}^{-1}$ of dry matter). Examples include $Fe, Mn, Cu, Mo, Zn, B, Cl,$ and $Ni$.

(D) The criteria for the essentiality of an element are as follows:
$(a)$ The element must be absolutely necessary for supporting normal growth and reproduction.
In the absence of the element,the plants do not complete their life cycle or set the seeds.
$(b)$ The requirement of the element must be specific and not replaceable by another element. In other words,the deficiency of any one element cannot be met by supplying some other element.
$(c)$ The element must be directly involved in the metabolism of the plant.

(D) Macronutrients are essential mineral elements required by plants in relatively large amounts (usually $10 \text{ mmol kg}^{-1}$ of dry matter).
These include Carbon $(C)$, Hydrogen $(H)$, Oxygen $(O)$, Nitrogen $(N)$, Phosphorus $(P)$, Sulphur $(S)$, Potassium $(K)$, Calcium $(Ca)$, and Magnesium $(Mg)$.
In the given options, option $(D)$ contains $C, H, Mg,$ and $N$, all of which are macronutrients.
Boron $(B)$, Manganese $(Mn)$, and Zinc $(Zn)$ are micronutrients required in smaller quantities.

(C) Plants absorb iron primarily in the form of ferric ions $(Fe^{3+})$.
Iron is an essential micronutrient required by plants in relatively larger amounts compared to other micronutrients.

(D) Macronutrients are essential elements that are required by plants in relatively large amounts.
According to the classification of mineral nutrients,macronutrients are generally present in plant tissues in concentrations of $10 \text{ m mole } kg^{-1}$ of dry matter or more.
Therefore,the minimum threshold for macronutrients is $10 \text{ m mole } kg^{-1}$ of dry matter.

(A) Plants require various mineral elements for their growth and development. These are classified as macronutrients and micronutrients based on their quantitative requirements. Nitrogen is a primary macronutrient that is required by plants in the greatest amount as it is a major component of proteins,nucleic acids,vitamins,and chlorophyll.

(A) There are $17$ essential mineral elements that have been discovered and are known to be required for plant growth and development.

(D) Macronutrients are essential elements required by plants in large amounts.
These include carbon,hydrogen,oxygen,nitrogen,phosphorus,sulphur,potassium,calcium,and magnesium.
Among the given options,phosphorus is a macronutrient,while zinc,boron,and nickel are micronutrients.

(D) Essential elements are grouped into four broad categories based on their functions:
$(i)$ Elements that act as components of biomolecules and are structural elements of cells: Carbon,Hydrogen,Oxygen,and Nitrogen.
$(ii)$ Elements that are components of energy-related chemical compounds in plants: Magnesium (in chlorophyll) and Phosphorus (in $ATP$).
$(iii)$ Elements that activate or inhibit enzymes: e.g.,Magnesium $(Mg^{2+})$ for RuBisCO and PEPCase.
$(iv)$ Elements that alter the osmotic potential of a cell: e.g.,Potassium $(K^+)$.
Since Hydrogen $(I)$,Oxygen $(III)$,and Nitrogen $(IV)$ are structural components of biomolecules,while Magnesium $(II)$ is primarily associated with energy-related compounds and enzyme activation,the correct answer is $I, III,$ and $IV$. However,looking at the provided options,the most accurate choice that includes the primary structural elements is $D$ (All except $II$).

(B) An essential element is defined by the following criteria:
$1.$ It is absolutely necessary for supporting normal growth and reproduction of plants.
$2.$ The requirement of the element must be specific and not replaceable by another element.
$3.$ The element must be directly involved in the metabolism of the plant.
$4.$ In the absence of the element,the plant cannot complete its life cycle or set seeds.
$5.$ The essential elements include $C, H, O, N, P, K, S, Mg, Ca, Fe, B, Mn, Cu, Zn, Mo,$ and $Cl$.

(C) Plants require various mineral elements for their growth and development. Among the essential nutrients,carbon,hydrogen,and oxygen are not considered mineral nutrients because they are not obtained from the soil.
Carbon is primarily obtained from atmospheric $CO_2$ through the process of photosynthesis.
Hydrogen is primarily obtained from $H_2O$ absorbed by the roots.
Oxygen is obtained from both $CO_2$ and $H_2O$.
Therefore,these three elements are obtained from both $CO_2$ and $H_2O$.

(D) The criteria for essentiality of an element are as follows:
$(i)$ The element must be absolutely necessary for supporting normal growth and reproduction. In the absence of the element,the plants do not complete their life cycle or set the seeds.
$(ii)$ The requirement of the element must be specific and not replaceable by any other element. In other words,deficiency of any one element cannot be met by supplying some other element.
$(iii)$ The element must be directly involved in the metabolism of the plant.
Since all three statements ($I, II,$ and $III$) define the criteria for essentiality of mineral elements,the correct answer is $I, II$ and $III$.

(D) Nitrogen is an essential element for all living organisms.
It is a major component of amino acids,which are the building blocks of proteins.
It is also a key constituent of chlorophyll,the pigment responsible for photosynthesis in plants.
Furthermore,nitrogen is present in various hormones (such as auxins and cytokinins) and vitamins (such as $B$-complex vitamins),which regulate plant growth and metabolism.
Therefore,all the given options are correct.

(C) The correct answer is $(c)$.
Essential elements can be grouped into four broad categories based on their diverse functions:
$(i)$ Essential elements that act as components of biomolecules and hence,structural elements of cells (e.g.,carbon,hydrogen,oxygen,and nitrogen).
$(ii)$ Essential elements that are components of energy-related chemical compounds in plants (e.g.,magnesium in chlorophyll,phosphorus in $ATP$).
$(iii)$ Essential elements that activate or inhibit enzymes (e.g.,$Mg^{2+}$ activates RuBisCO and PEPCase,while $Zn^{2+}$ activates alcohol dehydrogenase).
$(iv)$ Some essential elements can alter the osmotic potential of a cell (e.g.,potassium plays an important role in the opening and closing of stomata).

(B) Nitrogen $(N)$ is a critical element for all living organisms. It is a major constituent of proteins,nucleic acids ($DNA$ and $RNA$),amino acids,vitamins,hormones,chlorophyll,and many coenzymes. It is required by plants in the greatest amount and is absorbed mainly as $NO_3^-$ or $NH_4^+$.

(B) Carbon is a macronutrient,which is an essential component of all organic compounds.
Plants obtain carbon in the form of carbon dioxide $(CO_2)$ from the atmosphere,not from the soil.

(B) According to the criteria of essentiality for mineral elements,an element is considered essential only if it is indispensable for the normal growth and reproduction of the plant. It must be directly involved in the metabolism of the plant. Furthermore,the requirement of the element must be specific and not replaceable by another element. If a deficiency occurs,it can only be corrected by supplying that specific element. Therefore,the statement that an element must be replaceable by another element is incorrect.

(C) Out of $60$ elements found in the protoplasm of plants,$17$ are considered essential elements. These elements are required for the plant to complete its life cycle,and their deficiency causes specific symptoms. Additionally,there are some beneficial elements,but the number of strictly essential elements is $17$.

(A) Elements that are required by plants in large amounts are called macronutrients.
Macronutrients are generally present in plant tissues in concentrations of $10 \text{ mmol } kg^{-1}$ of dry matter or more.
Carbon and nitrogen are essential macronutrients,hence their concentration in plants is above $10 \text{ mmol } kg^{-1}$ of dry matter.

(B) Essential elements are those that are absolutely necessary for plant growth,reproduction,and completion of the life cycle.
$Mg$ (Magnesium) is a macronutrient essential for chlorophyll structure.
$Mo$ (Molybdenum) and $Ni$ (Nickel) are essential micronutrients for various enzymatic processes.
$Co$ (Cobalt) is considered a beneficial element,not an essential one,as it is required by some plants (like legumes for nitrogen fixation) but not by all plants.

(D) Essential mineral elements are classified into two categories based on their quantitative requirements: macronutrients and micronutrients.
Macronutrients are present in plant tissues in large amounts (generally in excess of $10 \text{ mmol kg}^{-1}$ of dry matter). Examples include $C, H, O, N, P, S, K, Ca,$ and $Mg$.
Micronutrients or trace elements are needed in very small amounts (less than $10 \text{ mmol kg}^{-1}$ of dry matter). These include $Fe, Mn, Cu, Mo, Zn, B, Cl,$ and $Ni$.
Therefore, among the given options, $Ni$ (Nickel) is a micronutrient, while $Ca, Mg,$ and $K$ are macronutrients.

(C) Beneficial elements are those that are required by higher plants in addition to the essential elements,such as $Na$,$Si$,$Co$,and $Se$. Potassium $(K)$ is classified as an essential macronutrient,not a beneficial element. Therefore,$K$ is the correct answer.

(D) ,$H$,and $O$ are considered non-mineral elements because they are obtained from $CO_2$ and $H_2O$ by plants.
Carbon $(C)$ is the fundamental backbone of all organic compounds,yet it is not classified as a mineral element because it is derived from the atmosphere and water rather than from the soil.

(D) According to Arnon and Stout $(1939)$,the criteria for essentiality of a mineral are:
$1$. The plant must be unable to complete its life cycle in the absence of the element.
$2$. The element must be specific and not replaceable by another element.
$3$. The element must be directly involved in the metabolism of the plant.
Since the element is essential for growth and development,it cannot be 'dispensable'. Therefore,being 'dispensable for growth' is not a criterion for essentiality.

(C) Critical elements are those essential plant nutrients that are most frequently deficient in the soil and limit plant growth. These include Nitrogen $(N)$,Phosphorus $(P)$,and Potassium $(K)$. Nickel is a micronutrient required in very small quantities and is not classified as a critical element. Therefore,Nickel is the odd one out.

(B) Silicon $(Si)$,Cobalt $(Co)$,Sodium $(Na)$,and Selenium $(Se)$ are classified as beneficial elements.
These elements are not considered essential for all plants but are required by certain higher plants for their growth and development.

(D) Essential elements are those that are required by plants for their growth,development,and reproduction. These are broadly classified into two categories based on their quantitative requirements:
$1$. Macronutrients: Required in relatively large amounts (e.g.,$C, H, O, N, P, K, S, Ca, Mg$).
$2$. Micronutrients: Required in very small amounts (e.g.,$Fe, Mn, Cu, Mo, Zn, B, Cl, Ni$).
Therefore,essential elements include both macro and micronutrients.

(C) The Assertion $(A)$ is correct because plants require specific mineral nutrients (essential elements) for their growth,development,and reproduction.
There are $17$ essential elements identified for plants.
The Reason $(R)$ is incorrect because these mineral nutrients cannot be synthesized by the plants themselves.
Plants must absorb these essential minerals from the soil,water,or atmosphere to fulfill their physiological requirements.

(A) $N, P, K$ (Nitrogen,Phosphorus,and Potassium) are known as critical elements because they are frequently deficient in the soil.
This deficiency occurs primarily because these elements are required by plants in relatively large quantities (macronutrients) and are also prone to loss from the soil through processes like leaching.
Therefore,both the Assertion and the Reason are correct,and the Reason provides a valid explanation for why they are termed critical.

(B) Plants absorb a wide variety of mineral elements from the soil,with over $60$ different elements found in plant tissues. However,only about $17$ elements are considered essential for plant growth and development.
Therefore,the Assertion is correct.
Some plants,known as hyperaccumulators,have the ability to absorb and accumulate high concentrations of heavy metals and toxic elements like gold,selenium,and even radioactive isotopes from the soil.
Therefore,the Reason is also correct.
However,the fact that some plants accumulate toxic minerals is a specific biological phenomenon and does not explain why all minerals found in plants are not essential. Thus,the Reason is not the correct explanation of the Assertion.

(B) Iodine is essential for the life of animals. It is required for the synthesis of the thyroxine hormone,which regulates the basal metabolic rate $(BMR)$. This hormone stimulates protein synthesis and,therefore,promotes the growth of body tissues. Plants do not require iodine for their physiological processes.

(B) $\Rightarrow$ Carbon is a fundamental component of all organic compounds. It is not obtained from the soil but is absorbed by plants in the form of $CO_{2}$ from the atmosphere. Its concentration in the atmosphere is approximately $0.03 \%$. Plants utilize this $CO_{2}$ during the process of photosynthesis to synthesize glucose and other organic molecules.

(B) The radioactive isotope of Strontium,specifically $Sr-90$,is a byproduct of nuclear fission in nuclear reactors and nuclear weapons testing. It is chemically similar to Calcium and can be absorbed by plants from the soil,subsequently entering the food chain. Therefore,it is commonly found in plants growing near nuclear test sites.