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Macronutrients: Elements which are present in large amounts in plant tissues are called macronutrients. They are in excess of 10 mmole per kg of dry matter. Carbon, hydrogen, oxygen, nitrogen, phosphorous, sulphur, potassium, calcium and magnesium are the macronutrients.

Micronutrients: Elements which are present in small amounts, i.e. less than 10 mmole per kg of dry matter are called micronutrients. Iron, manganese, copper, molybdenum, zinc, copper, boron, chlorine and nickel are the micronutrients.

Beneficial Elements: Apart from the 17 essential elements, many other elements are required by plants. For example; sodium, silicon, cobalt and selenium are required by higher plants.

Toxic Elements: If a mineral ion concentration in tissues reaches to a level that it reduces the dry weight of tissues by about 10%, the mineral then becomes toxic. This shows that any element can become toxic if it crosses a certain threshold in plants. 

Potassium is absorbed as K+ ions. It is abundant in meristems, buds, leaves and root tips.

Functions:

• It is involved in the opening and closing of stomata. It activates a number of enzymes.
• It is involved in protein synthesis
• It maintains turgidity of cells
• It maintains anion cation balance of cells

• Chlorosis – yellowing of leaves due to loss of chlorophyll caused by the deficiency of N, S, mg, Fe.
• Necrosis – Death of tissues, especially in leaves caused by the deficiency of Ca, Mg, Ca & K. 
• Delay in flowering caused by the deficiency of molybdenum, nitrogen, and sulphur.
• Dieback of roots caused by a deficiency of copper.
• Inhibition of cell division caused by a deficiency of potassium, calcium and nitrogen.

Examples: Anabaena, Nostoc

Denitrification is the process by which nitrate is converted into free nitrogen gas. The organisms involved are bacteria like pseudomonas and Thiobacillus.

 Following are the five deficiency symptoms and related minerals:

a. Yellowing of lower leaves: Magnesium deficiency 

b. Pale green leaves: Nitrogen deficiency 

c. Purple leaf tints with bronze or brown leaf edges: Potassium deficiency 

d. Reddish purple undersides of leaves: Phosphorous deficiency 

e. White deposits on leaves: Carbon dioxide deficiency

Magnesium 

• It helps to maintain ribosome structure 
• It activates enzymes of phosphate metabolism in respiration and photosynthesis 
• It is also involved in the synthesis of DNA and RNA.

For this, we need to tabulate all the available symptoms in different parts of the plant. Then the symptoms are compared with the symptom table; to arrive at a conclusion about the deficiency of a specific element.

Leghaemoglobin resembles the haemoglobin of vertebrates. Since it is present in the leguminous plants it is called as leghaemoglobin. It binds with oxygen and creates an anaerobic condition.

The deficiency symptoms tend to appear first in the young tissues whenever the elements are relatively immobile and are not transported out of the mature organs, for example, elements like sulphur and calcium are a part of the structural component of the cell and hence are not easily released.

Sulphur, Nitrogen, Phosphorous, Potassium.

Since each elements has one or more specific structural or functional role in plants, in the absence of any particular element, plants show certain morphological changes. These morphological changes are indicative of certain element deficiencies and are called deficiency symptoms. The deficiency symptoms vary from element to element and they disappear when the deficient mineral nutrient is provided to the plant. However, if deprivation continues, it may subsequently lead to the death of the plant. This way by administering different nutrients and observing the symptoms disappear we can find out experimentally the real deficient mineral element.

Carbon, hydrogen, oxygen and nitrogen.

H₂ PO_4- and HPO^₄2-

• It is necessary for the formation of middle lamella during cell division.
• It is also needed for the formation of spindle fibres.

(i) Iron deficiency:

It is a plant disorder also known as lime induced chlorosis. A deficiency in the soil is rare but iron can be unavailable for absorption if soil PH is not between 5 and 6.5. A common problem is when the soil is too alkaline. Also, iron deficiency can develop if the soil is too waterlogged or has been overfertilised. Iron is needed to produce chlorophyll, hence its deficiency causes chlorosis.

Symptoms:

Leaves turning yellow or brown in the margins between the veins which may remain green, while young leaves may appear to be bleached. Fruit would be of poor quality.

Treatment:

By choosing appropriate soil for the growing conditions or by adding well-rooted manure or compost.

(2) Potassium deficiency:

Plants require potassium ions for protein synthesis and for the opening and closing of stomata, which is regulated by proton pumps to make surrounding guard cells either turgid or flaccid. A deficiency of potassium ions can impair a plant’s ability to maintain these processes.

Symptoms:

Brown scorching and curling of leaf tips and yellowing of leaf veins. Purple spots may appear on the leaf undersides.

Prevention and cure:

Feeding with homemade comfrey liquid, adding seaweed meal, composted bracken or other organic potassium-rich fertilizer. Adding plants of well rotted compost.

(3) Calcium deficiency:

Caused by insufficient calcium in the growing medium, but is more frequently a product of a compromised nutrient mobility system in the plant.

Symptoms:

Stunted plant growth, necrotic leaf margins on young leaves or curling of the leaves and eventual death of terminal buds and root tips. Treatment: Adding agricultural lime to acid soils, aiming at a P H of 6.5. Adding organic matter to the soil to improve its moisture retaining capacity.

(4) Nitrogen deficiency:

Occurs when woody material such as sawdust is added to the soil. Soil organisms will utilise any nitrogen in order to break this down; thus making it temporarily unavailable to growing plants.

Symptoms:

Poor plant growth, leaves are pale green or yellow in case of brassicas. Leaves are said to be etiolated with reduced chlorophyll. Following and fruiting are delayed. Prevention and control: using grass movings as a mulch, or foliar feeding with manure and building up levels of organic matter in the soil, Leguminous green manures will fix additional nitrogen from the atmosphere.

(5) Manganese deficiency:

Most common in poorly drained soils also where organic matter levels are high.

Symptoms:

yellowing of leaves with smallest leaf veins remaining green to produce a chequered effect. Brown spots appear on leaf surfaces and severely affected leaves turn brown and wither.

Iron – Boron, Manganese, Molybdenum.

Macronutrients:

Generally present in plant tissues in large amounts. The macronutrients include carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, potassium calcium and magnesium. Of these carbon, hydrogen and oxygen are mainly obtained from CO₂ and H₂O, while the others are absorbed from the soil as mineral nutrition.

Micronutrients:

Also called Trace elements are needed in very small amounts. These include iron, manganese, copper, molybdenum, zinc, boron, chlorine and nickel.

Beneficial nutrients:

Include sodium, silicon, cobalt and selenium. They are required by higher plants.

Toxic elements:

Any mineral ion concentration in tissues that reduces the dry weight of tissues by about 10 percent is considered toxic. The toxicity symptoms are difficult to identify. Micronutrients in excess causes toxicity.

Essential elements:

Four categories on the basis of their diverse functions.

(a) As components of biomolecules and hence structural elements of cells.

e.g. carbon, hydrogen, oxygen and nitrogen.

(b) As components of energy related chemical compounds in plants.

e.g. magnesium in chlorophyll

(c) Elements that activate or inhibit enzymes, e.g. Mg²⁺ is an activator for both ribulose bisphosphate carboxylase oxygenase and phosphoenol pyruvate carboxylase.

(d) Elements that alter the osmotic potential of a cell.

e.g. Potassium in opening and closing of stomata.

Following micronutrients are involved in many metabolic activities of the plants: 

(i) Boron (B) is involved in the formation of pectin in the cell wall, in the translocation of carbohydrates absorption of water and calcium. 

(ii) Copper (Cu), being an essential component of plastocyanin, is involved in the electron transport and plays a role in photosynthesis. 

(iii) Manganese (Mn) and molybdenum plays an important role in nitrogen metabolism. 

(iv) Zinc (Zn) helps in the synthesis of Indole Acetic Acid (IAA).

As catalysts in the enzymatic reactions : Zinc, copper and manganese act as enzyme activators for various enzymatic reactions in plant cells. As for example: 

(i) Zinc activates many enzymes such as lactic dehydrogenase, carboxy peptidases, glutamic acid dehydrogenase and alcohol dehydrogenase. 

(ii) Manganese acts as an activator for the enzymes which are involved in decarboxylation reaction and dehydrogenation during respiration.

Copper, Iron. 

on channels are transmembrane 

Mineral deficiency of plant A and B: 

1. Plant A is deficient of the mineral molybdenum (Mo). 

2. Plant B is deficient of the mineral zinc (Zn).

Nitrogenase . 

Class 11 Biology MCQ Questions of mineral nutrition, you will learn exhaustively about essential mineral nutrients that plants need for development and growth. What’s more, you will likewise figure out how plants retain these fundamental supplements, nutrients, deficiency symptoms, and the significance of nitrogen as a micronutrient and biological nitrogen fixation. We have provided Class 11 MCQ Questions with Answers to help students with understanding the concept well.

Check here and practice MCQ Questions for Class 11 Biology Mineral Nutrition with Answers were arranged dependent on the most recent exam pattern. The accompanying MCQ Questions for class 11 Biology and minor components will empower you to acquire more clarity of the concepts discussed within this chapter. Besides that, practicing these questions will likewise assist you with revising this Chapter altogether before examinations.

Practice MCQ Questions for class 11 Biology Chapter-Wise

1. The formation of first stable product of nitrogen fixation is catalyzed by the enzyme

(a) dehydrogenase
(b) nitrogenase
(c) isomerase
(d) none of these

2. Chlorosis will occur if a plant is grown in

(a) dark
(b) shade
(c) strong light
(d) Fe – free medium

3. Which one of the following mineral elements plays an in biological nitrogen fixation?

(a) Copper
(b) Manganese
(c) Zinc
(d) Molybdenum

4. Oxygen scavengers present in root nodules of legumes is

(a) haemoglobin
(b) leg haemoglobin
(c) cyano haemoglobin
(d) none of these

5. Insectivorous plants grow where

(a) There is carbohydrate-deficient soil
(b) There is nitrogen-deficient soil
(c) Vitamin c is required
(d) Hormones are required

6. Toxicity of which element leads to the appearance of brown spots on leaves

(a) Mg
(b) Mn
(c) Fe
(d) Cu

7. Exanthema is due to deficiency of

(a) B
(b) Mo
(c) Mn
(d) Cu

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

(a) molybdenum
(b) manganese
(c) magnesium
(d) nitrogen

9. Death of stem and root tips occur due to deficiency of

(a) Calcium
(b) Nitrogen
(c) Carbon
(d) Phosphorus

10. Mineral associated with cytochrome is

(a) Cu 
(b) Mg 
(c) Fe and Mg 
(d) Fe and Cu

11. The association between blue-green algae and fungi occurs in 

(a) lichens
(b) symbiosis
(c) cannibalism
(d) mycorrhiza

12. Which element is required by the plants for uptake and utilization of calcium and carbohydrate translocation?

(a) Manganese
(b) Boron
(c) Chlorine
(d) Selenium

13. How many ATP molecules are required to biologically fix one molecule of nitrogen into two molecules of ammonia?

(a) 4
(b) 8
(c) 12
(d) 16

14. When the plants are grown in magnesium-deficient but urea rich soil, the symptoms expressed are:

(a) yellowish leaves
(b) colourless petiole
(c) dark green leaves
(d) shoot apex die

15. Deficiency symptoms of nitrogen and potassium are visible first in

(a) senescent leaves
(b) young leaves
(c) roots
(d) buds

16. The most abundant intracellular cation is

(a) \(Na^+\)
(b) \(Ca^{2+}\)
(c) \(H^+\)
(d) \(K^+\)

17. Best defined function of manganese in green plants is

(a) photolysis of water
(b) Calvin cycle
(c) nitrogen fixation
(d) water absorption

18. An organism used as a biofertilizer for raising soyabean crops is

(a) Azospirillum
(b) Rhizobium
(c) Nostoc
(d) Azotobacter

19. Obligate parasites are organisms that 

(a) Are saprophytes but can also become parasites.
(b) Are pests but can also become saprophytes.
(c) Consume only dead and organic matter.
(d) Consume living host.

20. Among the elements given below, which one has not yet been proved as essential for plants?

(a) Zinc
(b) Iron
(c) Potassium
(d) Sodium

21. The middle lamella mainly contains

(a) Na
(b) Mg
(c) K
(d) Ca

22. Non-symbiotic nitrogen-fixing prokaryote is

(a) Frankia
(b) Acetobacter
(c) Rhizobium
(d) Azotobacter

23. Which one of the following organism help in absorption of phosphorus from soil by plants

(a) Glomus
(b) Frankia
(c) Rhizobium
(d) Anabaena

24. The deficiencies of micronutrients, not only affect the growth of plants but also vital functions such as photosynthetic and mitochondrial electron flow. Among the list given below, which group of three elements shall affect most, both photosynthetic and mitochondrial electron transport? 

(a) Co, Ni, Mo
(b) Ca, K, Na
(c) Mn, Co, Ca
(d) Cu, Mn, Fe

25. Grey spots of oat are caused by deficiency of

(a) Fe
(b) Cu 
(c) Zn
(d) Mn

Answer:

 1.Answer: (b) nitrogenase

Explanation: The nitrogen fixation bacterium has nitrogenase enzyme, which is found in the leguminous plant root nodules. A multi-step reaction catalyzed by the bacterial nitrogenase enzyme converts the free nitrogen gas to ammonium ions.

2. Answer: (d) Fe – free medium

Explanation: Chlorosis is normally a symptom of the plant disease in which the plant gets pale or yellow in color from green color. It is the failure of the green pigment chlorophyll because of the lack of nutrients or oxygen in the plan leaves. Chlorosis is mainly caused by the deficiency of the iron in the plant leaves.

3. Answer:(d) Molybdenum

Explanation: Molybdenum (Mo) is a component of enzyme nitrogenase and thus, plays an important role in biological nitrogen fixation.

4. Answer: (b) leg haemoglobin

Explanation: Leghaemoglobin is present in the root nodules of legume plants. This functions like a scavenger for oxygen. - Leghaemoglobin is a scavenger of oxygen that protects nitrogenase during fixation of nitrogen.

5. Answer: (b) There is nitrogen-deficient soil

Explanation: Insectivorous plants commonly grow in areas where the soil is deficient in Nitrogen. Insectivorous plants are the plants that derive some or most of their nutrients (but not energy, which they derive from photosynthesis) from trapping and consuming animals or protozoans, typically insects and other arthropods.

6. Answer: (b) Mn

Explanation: The toxicity of manganese causes a decreased uptake of both Mg and Fe, inhibition of Calcium relocation as well as inhibition of binding of manganese with various enzymes. This causes decreased chlorophyll production, and in turn, causes chlorotic veins and brown spots.

7. Answer: (d) Cu

Explanation: Copper deficiency is responsible for exanthema in citrus. Fruits reveal patches of gum around the central pith. Exudation of the gum can also be observed on the rind.

8. Answer: (a) molybdenum

Explanation: The condition known as " whiptail .. in cauliflower and broccoli has been shown to be due to a deficiency of molybdenum (Davies, 1945).

9. Answer: (a) Calcium

Explanation: "Calcium" is essential for the growth of root tips. Calcium is present in the cell walls in the form of 'calcium pectate'. It helps in holding the plant's cells together and for the growth of the new cells.

10. Answer: (d) Fe and Cu

Explanation:  Minerals associated with cytochrome are Fe and Cu. Cytochromes are Iron-containing (Iron porphyrin protein) electron transferring (the electrons are picked up and released by Fe) except Cytochrome-\(a_3.\)

11.Answer: (a) lichens

Explanation: In lichens, the association between an algae and a fungus is considered to be a symbiotic one. In this association, algae provide food to fungi.

12.Answer: (b) Boron

Explanation:Plants require boron in leaves and seeds. It is required for uptake and utilization of calcium, pollen germination, and cell differentiation, and carbohydrate translocation.

13. Answer: (d) 16

Explanation: one molecule of dinitrogen requires 16 ATP molecules to form 2 ammonia molecules.

14. Answer: (a) yellowish leaves

Explanation: Deficiency of Mg causes chlorosis i.e., yellowing of leaves. Thus a plant growing in magnesium-deficient soil would show chlorosis inspite of being sprayed with urea (nitrogen).

15.Answer: (a) senescent leaves

Explanation: Deficiency symptoms of nitrogen and potassium are visible first in senescent (older) leaves. Due to nitrogen deficiency, the symptoms include poor plant growth, and leaves become pale green or yellow because they're unable to form sufficient chlorophyll.

16. Answer: (d) \(K^+\)

Explanation:The major cation in the intracellular fluid is potassium. These electrolytes play an important role in maintaining homeostasis.

17. Answer: (a) photolysis of water

Explanation:Manganese is used for the photolysis of water to produce oxygen and electrons during the light reaction of photosynthesis. It is the phenomenon of breaking up water into hydrogen and oxygen in the illuminated chloroplast. It acts as an essential cofactor.

18. Answer: (b) Rhizobium

Explanation: Rhizobium is a bacteria that live inside the root nodules of leguminous plants. They form a symbiotic association with the plant. They fix the atmospheric nitrogen for the plants. They are used in soybean and pea plant fields as biofertilizers.

19. Answer: (d) Consume living host

Explanation:An obligate parasite or holoparasite is a parasitic organism that cannot complete its life cycle without exploiting a suitable host. If an obligate parasite cannot obtain a host it will fail to reproduce.

20. Answer: (d) Sodium

Explanation:The 17 essential elements of the plants are divided into two major categories called micronutrients and macronutrients. The element which is not so essential consists of an atomic number 16. So, the correct answer is 'Sodium'.

21. Answer: (d) Ca

Explanation: The middle lamella is made up of calcium and magnesium pectates. In a mature plant cell, it is the outermost layer of the cell wall.

22. Answer:(d) Azotobacter

Explanation: Azotobactera is non-symbiotic or free-living bacterium. It helps in the nitrogen fixation.

23. Answer: (a) Glomus

Explanation: Many members of the genus Glomus form mycorrhiza. The fungal symbiont in these associations absorbs phosphorus from soil and passes it to the plant.

24.Answer: (d) Cu, Mn, Fe

Explanation: Cu (copper), Mn (manganese), and Fe (iron) are those micronutrients, which affect both photosynthesis and mitochondrial electron transport because they are the main constituents of various electron carriers.

25. Answer:(d) Mn

Explanation: The deficiency of Manganese leads to a grey spot of Oat disease. In this condition, the brown elongated speck and streaks are found in panicles. Development of the root system is poor.

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Mechanism of Nitrogen fixation :

• An enzyme Nitrogenase (Mo-Fe protein complex) catalyses the conversion of N₂ into NH₃ in root nodules.
• Enzyme Nitrogenase is highly sensitive to molecular oxygen and requires anaerobic condition to function.
• Anaerobic condition in root nodules is provided by a pink coloured pigment called as leg haemoglobin which acts as oxygen scavenger by binding with O₂. Leg-haemoglobin is product of interaction between Rhizobium & leguminous plant. Either of two cannot have it alone. 

Nitrification is conversion of ammonia into Nitrate (oxidation of NH₃ into NO₃^-). It is carried out in two steps by Nitrifying bacteria (chemoautotrophs).

• NH₃(Nitrite) → NO₂^- (by Nitrosomonas,Nitrosococcus bacteria)
• NO₂^-(Nitrite) → NO₃^-(Nitrate) (by Nitrobacter)

Ammonification is conversion of organic nitrogen (dead plants & animals) into ammonia.

Steps of Nodule Formation : 

Rhizobium in soil interacts with roots of leguminous plants.

                          ↓

Rhizobia multiply, colonise and get attached to epidermal & root hair cells.

                            ↓

Curling of root hair & invasion of bacteria into root hair. 

                            ↓

Produce infection thread & carry bacteria into root cortex.

                             ↓

Initiate nodule formation in the cortex.

(i) The soil in the pot will change its weight due to accumulation of minerals, fertilizers, capillary and hygroscopic water and the micro-organisms. 

(ii) The plants increase its weight due to manufacturing of food during photosynthesis. 

(iii) Plant depends largely on air, water and soil organisms in the soil of pot to fulfil its need. 

(iv) This results in the growth of plant by increasing the weight of soil in the pot.

Different macronutrients and their functions are : 

(i) Carbon : It is the major component of carbohydrates and other cellular constituents. 

(ii) Oxygen : It is an important component of carbohydrates and other structural constituents of the cells. 

(iii) Magnesium: It is an essential component of chlorophyll and is involved in binding of ribosome components. It acts as enzyme activator in those cases which are concerned with phosphate metabolism. 

(iv) Calcium : 

(a) Synthesizes calcium pectinate, the constituents of middle lamella in the cell wall. 

(b) It helps in translocation of carbohydrates. 

(c) It regulates cell permeability. 

(d) It helps in lipid metabolism. 

(v) Nitrogen: 

(a) It is an important constituent of protoplasm and protein. 

(b) It is found in amino acids, NAD, NADP, purines, pyrimidines, chlorophyll enzyme etc.

(vi) Phosphorus: 

(a) An important constituent of cell membrane, certain proteins, all nucleic acid and nucleotides. 

(b) It is present in AMP, ADP ATP GDP and GTP and plays an important role in the energy transfer of photosynthesis and respiration. 

(c) Essential for all phosphorylation reactions.

Minerals like Sodium,Silicon, Cobalt and Selenium are not included in the list of essential nutrients but are required by some plants, these minerals are placed in the list of unclassified minerals. These minerals play specific roles for example, Silicon is essential for pest resistance, prevent water lodging and aids cell wall formation in Equisetaceae (Equisetum), Cyperaceae and Gramineae.

 Appearance of deficiency also depends on the mobility of the element in the plant. Some elements are actively mobilized in plants and are exported to young developing tissues. Deficiency of such elements first appears in the older tissues. For example; the deficiency symptoms of nitrogen, potassium and magnesium are first seen in the senescent leaves. This happens because these elements are mobilized to younger leaves.

Rhizobium bacteria need symbiotic association with legume plants to carry out nitrogen fixation. Root nodules contain the necessary enzymes for nitrogen fixation and thus enable rhizobium to fix nitrogen. The enzyme nitrogenase facilitates the conversion of nitrogen into ammonia which is the first stable product of nitrogen fixation. Ammonia is then converted into glutamic acid. Glutamic acid is then utilised by plants to make amino acids; which are then utilised to make protein. 

The deficiency symptoms tend to appear first in the young tissues whenever the elements are relatively immobile and are not transported out of the mature organs, for example, elements like sulphur and calcium are a part of the structural component of the cell and hence are not easily released.

Rhizobia are unique because they live in a symbiotic relationship with legumes.

Necessary conditions:

• Requires a strong reducing agent and energy in the form of ATP.
• The enzyme nitrogenase which is very sensitive to oxygen is required.
• The processes take place in anaerobic environment 
• The energy is provided by the respiration of host cells.

Reduction of nitrogen to ammonia by living organisms is called biological nitrogen fixation. The enzyme, nitrogenase which is capable of nitrogen reduction is present exclusively in prokaryotes. Several types of symbiotic biological nitrogen fixing associations are known. The most common association on roots is as nodules. Their role in N₂– fixation is to supply the plants with nitrogenase that converts nitrogen to amino acids.

Two examples of symbiotic mode of nutrition: 

1. Lichens: It is a mutual association of Algae and Fungi. Algae prepares food and fungi absorbs water and provides thallus structure. 

2. Mycorrhizae: Fungi associated with roots of higher plants including Gymriosperms. eg: Pinus.

(d) all of these

Movement of ions into cells is called influx while movement of ions out of the cells is called efflux.

Magnesium is a constituent of the ring structure of chlorophyll.

The mineral elements are required by higher plants. 

General functions of mineral elements are given below: 

(i) Constituents of plant body : Various mineral elements become permanent constituents of molecules found in the protoplasm and cell wall. Elements like carbon, hydrogen and oxygen are used in the formation of carbohydrates. Nitrogen is an essential component of all amino acids, protein, nucleic acids, chlorophyll, auxins, cytokinins and vitamins. Calcium is a constituent of calcium pectate of middle lamella. Magnesium is an essential part of the chlorophyll molecule and also activates certain enzymes. 

(ii) Osmotic potential of cells: The osmotic potential of a cell is maintained by the inorganic salts present in the cell sap. Osmotic potential is required for water absorption and maintenance of cell's turgidity. 

(iii) Permeability of cytoplasmic membranes: The permeability of cytoplasmic membranes is affected by the presence of various cations and anions in the external medium. Monovalent cations commonly increase the membrane permeability, while divalent cations decrease the same. 

(iv) Toxic effects: Many minerals elements in their ionic form produce a toxic effect on the protoplasm Important among them are arsenic, copper, mercury etc. 

(v) Catalytic effects: Several mineral elements participate in catalytic systems of plants. For example, calcium, magnesium, manganese, sodium, potassium and chlorine serve as cofactors at enzymes.

Iron is required for synthesis of cytochromes.

Ferrodoxin and cytochromes.

Nitrogenase.

Rhizobium is the best known symbiotic nitrogen fixing bacterium.

Leghaemoglobirn.

Leghaemoglobin

When atmospheric nitrogen fixation takes place by free living bacteria or cyanobacteria without showing any mutual relationship with any other species is called non-symbiotic nitrogen fixation. E.g. Azotobacter,Anabaena, Nostoc.

Magnesium is absorbed as Mg²⁺ ions

Functions

• It forms the central atom of porphyrins ring of chlorophyll.
• It maintains the ribosome structure 

Deficiency symptoms:

• Chlorosis and necrosis Premature leaf fall.

Correct Answer is: (c) Calcium

Rhodospirillum and Bacillus.

Azotobacter and Beijernickia.