12- MINERALS NUTRITION

CHAPTER NO.12 MINERAL NUTRITION

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INTRODUCTION:Soil provides anchorage, air, water and essential minerals to the plants

growing in it. An important function of soil is to store and supply nutrients to

plants. The ability to perform this function is referred to as soil fertility.

SOIL AS A RESERVOIR OF ESSENTIAL ELEMENTS

Majority of Nutrients that are essential for the growth and development of plants become available to the roots due to weathering and breakdown of rocks.

Since the nutrients are derived from the rock minerals, their role in plant nutrition is referred to as Mineral Nutrition.' Soil colloids are particles that retain nutrients for release into the

soil solution for uptake by roots.Soil colloids maintain reservoir of soluble nutrients in the soil. Clay are part of soil and humus form colloidal particles in the soil. The colloids carry a large number of charges on their surface as well as

they have large surface area for interaction with mineral elements in

soil. The Charged surfaces bind large number of ions especially positively charges cations from soil solution. This is the most important property of soil.

Soil not only supplies minerals but also harbours nitrogen fixing bacteria, other microbes, hold water, supplies air to the roots and act as matrix that stabilises the plant.Soil also has a large number of microorganisms that not only decompose organic remains but also release the minerals bound in organic matter.Nz fixing bacteria increase the usable nitrogen content of soil.Soil is able to maintain a regular supply of minerals partly by the

activity of decomposers and partly by slow breakdown of rocks.This also replenishes the natural slow erosion of top layers of soil.Due to agriculture, there is a more withdrawal of mineral nutrients from soil than their natural replenishment Therefore there is often deficiency of essential minerals Artificial fertilizers are added to remove the same.

Both macronutrients (N,P,K,S etc.)and micronutrients (Cu,Zn, Fe,Mn etc.) for components of fertilizers

and supplied when there is deficiency of nutrients as per need.

LET US KNOW WHAT WE HAVE LEARNT !

1. Assertion Statement

1: Soil serves as a reservoir of essential elements.Reason Statement

2: Soil develops, over the years, through physical and chemical weathering of rocks.

a. Both Assertion and Reason are correct and Reason is the correct explanation

for Assertion.

b. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

c. Assertion is correct but Reason is incorrect.

d. Both Assertion and Reason are incorrect.

2. Plants can be grown in:

a. Soil with essential nutrients.

b. Water with essential nutrients.

c. Either water or soil with essential nutrients.

d. Water or soil without essential nutrients.

3. A number of minerals like Ca, Mg and K are held over the surface of clay

particles because the latter are:

a. Negatively charged

b. Positively charged

c. Neutral

d. Having both positive and negative residual valencies

4. Phosphorous and nitrogen ions generally get depeleted in soil because they usually occur as:

a. neutral ions

b. negatively charged ions

c. positively charged ions

d. Both positively and negatively charged but disproportionate mixture.

5. Identify a micronutrient for plants amongst the following:

a. Potassium

b. Phosphorus

c. lron

d. Sulphur

(B) TRUE/FALSE:

1. Nitrogen as a Nutrient is highly immobile in the plants.

2. Rhizobium does not play any role in maintaining nutrient content of soil.

3. To overcome the deficiency of essential mineral; artificial fertilizer are

added to remove the same.

(C) FILL IN THE BLANKS:

1. Nutrients are available to the roots by and of rocks.

2. maintain reservoir of soluble nutrients in the soil.

3. are the elements, without which, the plants will not be able to complete its life cycle.

ANSWER KEY: PARTA

(A) MCQs:

Answer 1: (b) Explanation: Soil seves as a reservoir of essential elements. More

than sixty essential elements are found in soil. It is the upper weathered humus

containing part of Earth's surface which sustains terrestrial plant life. Weathering

or breaking of rock into fine powder can occur due to atmospheric changes,

mechanical forces, chemical changes and biological breakdown over the years.

Answer 2: (d) Explanation: Plants cannot grow in water or soil without essential

nutrients because lack of nutrients will lead to no growth.

Answer 3: (a) Explanation:Yes the elements like Ca, Mg, K are held over clay

particles as these elements possess the positive charge, Ca, Mg, K and clay

particles bear negative charge, so due to the electrostatic attraction, these

elements get attach to the clay particles.

Answer 4: (b) Explanation: Phosphorous and nitrogen ions generally get depleted in soil because they usually occur as negatively charged ions. Both the

elements are essential for plants and acts as macromolecules which are required

in large quantities.

Answer 5: (c) Explanation: In the soild, phosphorus and nitrogen are present as

negatively charged ions, e.g NOs NOz etc ions. These are usually supplied by

fertilisers as urea.

(B) TRUE/FALSE:

Ans. 1: (False) Explanation: Nitrogen is highly mobile.

Ans. 2: (False) Explanation: Rhizobium converts nitrogen into usable form and

can be available to the plants.

Ans. 3: (True) Explanation: Fertilizer replace the nutrients that crops remove

from the soil.

(C) FILL IN THE BLANKS:

1. Weathering and Breakdown

2. Colloids

3. Mineral Explanation : A mineral element is considered essential to plant

growth and development if the element is involved in plant metabolic functions and the plant cannot complete its life cycle without the element.

PART B: SHORT ANSWER TYPE QUESTIONS:

1. Define Mineral Nutrition.

2. A farmer adds Azotobacter culture to soil before sowing maize. Which

mineral element is being replenished?

3. Differentiate between micronutrients and macronutrients.

PART C: LONG ANSWER TYPE QUESTIONS:

1. Explain soil as a reservoir of essential mineral element?

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INTRODUCTION:METABOLISM OF NITROGEN

The sub-topics which we will study in this Daily Dose assignment are;

1. NITROGEN CYCLE

2. NITROGEN FIXATION

(A) ABIOLOGICAL NITROGEN FIXATION

(B) BIOLOGICAL NITROGEN FIXATION

3. REQUIREMENTS OF BIOLOGICAL FIXATION OF NITROGEN

4. NODULE FORMATION

5. BOCHEMICAL PROCESS

1.NITROGEN CYCLE

Unusable nitrogen ——————__» Usable nitrogen

(78% in air) (ammonia)

1. Lightning converts NITROGEN to AMMONIA.

2. Nitrogen fixers e.g. Rhizobium, found in roots of leguminous plants converts

NITROGEN to AMMONIA.

3. Nitrogen is a constituent of amino acids, proteins, hormones,chlorophylis and many of the vitamins.

4. Nitrogen is a limiting nutrient for both natural and agriculture eco-systems.

The process of conversion of nitrogen to ammonia is known an Nitrogen fixation.

TYPES OF NITROGEN FIXATION

A. ABIOLOGICAL NITROGEN FIXATION

B. BIOLOGICAL NITROGEN FIXATION

(A) ABIOLOGICAL NITROGEN FIXATION:

1. Industrial fixation: Preparation of synthetic ammonia in industries.Eg.Haber's process 500°C Net3H, ———®__ 2NH,1000 atmosphere

2. Natural fixation: During electrical discharges and lightning in nature.

O.N-+O, ——*2NO —— 2NO,The overall equation :The general equation for nitrogen fixation may be described as follows:+

N.+8e+8H+16ATP —> __ 2NHo+H2+16ADP+16Pi

(B) BIOLOGICAL NITROGEN EIXATION:Reduction of nitrogen to ammonia by living organisms called Biological nitrogen fixation.

The enzyme, nitrogenase which is capable of nitrogen reduction is present exclusively in prokaryotes.Such microbes are called Nitrogen-fixers.

EXAMPLES OF NITROGEN FIXERS:

1. Free living microbes

2. Symbiotic microbes

3. REQUIREMENTS OF BIOLOGICAL FIXATION OF NITROGEN

(i) Molecular nitrogen

(ii) A reducing power to reduce nitrogen like:reduced FAD (Flavin adenine dinucleotide) and reduced NAD (Nicotinamide Adenine Dinucleotide).

(iii) A source of energy (ATP)

to transfer hydrogen atoms from NADH: or FADH, (from photosynthesis) to

dinitrogen.

(iv) Enzyme nitrogenase

(v) Compounds for trapping the ammonia formed since it is toxic to cells.

LEG-HAEMOGLOBIN LEG-HAEMOGLOBIN is a pinkish color pigment present in the root

nodules of leguminous plants.It is an oxygen scavenger and protects the Nitrogenase enzyme fromaction of oxygen.

AMMONIFICATION:- Decomposition of organic nitrogen of dead plants and animals into ammonia is called ammonification.

DENITRIFICATION:- Conversion of nitrates into free nitrogen is called denitrification.

NITRIFICATION:- Ammonia is first oxidized to nitrite by the bacteria Nitrosomonas or Nitrococcus. The nitrite is further oxidized to nitrate with the help of the bacterium Nitrobacter. These steps are called Nitrification. These nitrifying bacteria are CHEMOAUTOTROPHS.

4. NODULE FORMATION

Roots of a legume secrete chemical attractants like flavonoids and betaines ( Zwitter ion non — protein amino acids)Bacteria collect over the root hair, release node factor that cause curling of root hair around the bacteria and degradation of cell

wall and formation of a thread enclosing the bacteria.Infection thread grows along with multiplication of bacteria. It

branches and it sends come to lie opposite protoxylem points of vascular strand.

The infected cortical cells differentiate and start dividing. It produces swelling or nodules.Nodule formation is stimulated by AUXIN produced by cortical cells and CYTOKININ liberated by invading bacteria.

The infected cells enlarge, bacteria stops dividing and form irregular polyhedral structure called bacteriods.

5.BIOCHEMICAL PROCESS

Nz ——___——_} NH;

N.+nitrogenase ——————_) N-H.Diazene

N-H-Diazene ———> N2HaHydrazine

N-HaHydrazine ———> 2NH;Ammonia

Ammoniaconvertedtoaminoacids,asitistoxic.

Ammonia synthesis by nitrogenease requires a very high input ofenergy (8 ATP for each NHs produced). The energy required,

thus, is obtained from the respiration of the host cells.

LET US KNOW WHAT WE HAVE LEARNT :-

PART(A)-VERY SHORT ANSWER TYPE QUESTIONS :-

(a) MULTIPLE CHOICE QUESTIONS:-

1. The process of conversion of nitrogen to ammonia is known as:

(a)Nitrogen fixation

(b) Nitrification

(d) Dentrification

2. Conversion of nitrates into free nitrogen is called:

(a)Nitrogen fixation

(b) Nitrification

(d) Dentrification

3. Decomposition of organic nitrogen of dead plants and animals into

ammonia is called:

(a)Nitrogen fixation

(b) Nitrification

(d) Dentrification

4. Nitrogen is constituent of:

(a)Aminoacids

(b) Hormones

(d) All the above

5. The enzyme which play role in Nitrogen fixation is:

(a) Nitrogenase

(b) Leg-haemoglobin

(d) All the above

(b) FILLIN THE BLANK:-

1. Nitrogen is nutrient for both natural and agriculture eco-systems.

2. Nitrifying bacteria are .

3. Nitrogen fixation are of types.

(c) TRUE/EALSE:-

1. Conversion of nitrates into free nitrogen is called denitrification.

2. Rhodospirillum is aerobic.

ANSWER KEY: PART(A)

(a) MULTIPLE CHOICE QUESTIONS :-

1. (a)Nitrogen fixation. The process of conversion of nitrogen to ammonia

is known an Nitrogen fixation.

2. (d)Dentrification. Conversion of nitrates into free nitrogen is

called denitrification.

3. (c)Ammonification.Decomposition of organic nitrogen of dead plants and

animals into ammonia is called ammonification.

4. (d) All the above. Nitrogen is a constituent of aminoacids,

proteins, hormones, chlorophylls and many of the vitamins.

5. (a)Nitrogenase. Nitrogenase enzyme which play role in Nitrogen fixation.

(b) FILL IN THE BLANK:-

1. Nitrogen is a limiting nutrient for both natural and agriculture eco-systems.

2. Nitrifying bacteria are chemoautotrophs.

3. Nitrogen fixation are of two types.

(c) TRUE/FALSE:-

1. True.Conversion of nitrates into free nitrogen is called denitrification.

2. False.Rhodospirillum is an aerobic.

(B) SHORT ANSWER TYPE QUESTIONS

Ques1. What is leg-haemoglobin? What is its role?

Ques2. What is Nitrification?

(C) LONG ANSWER TYPE QUESTIONS

Ques1. Explain the mechanism of nitrogen fixation.

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RECAPITULATION:In this chapter of “Mineral Nutrition”, we have learnt;Mineral nutrition is the study of source, mode of absorption, distribution and

metabolism of various inorganic substances (minerals) by plants for their growth,

development, structure, physiology and reproduction.

1. Two types of nutrients are there:Macronutrients are present in plants tissues in larger quantity.Micronutrients or trace nutrients are required in vary small quantity.

2. Deficiency symptoms of essential elements.

3. Mechanism of absorption of elements

4. Metabolism of nitrogen- Nitrogen cycle, Biological nitrogen fixation

“LETS US KNOW WHAT WE HAVE LEARNT”

NCERT EXERCISE QUESTIONS WITH SOLUTIONS

Q1. ‘All elements that are present in a plant need not be essential to its

survival’. Comment.

Ans 1. Yes, out of 105 elements absorbed by plants only about 17 elements are

essential for plant growth and survival. However all the elements found in plants are not essential for them. The non-essential elements enter plants due to their common pathway with essential elements and special conditions of the soil which make htem soluble.

Q2. Why is purification of water and nutrient salts so important in studies

involving mineral nutrition using hydroponics?

Ans 2. Hydroponics is a method of growing plants in the nutrition solution in the

absence of soil. There are plenty of impurities in impure water in the form of

soluble minerals that are dissolved in it. If this water is used as a solution culture

to grow plants in hydroponics, these impurities will interfere with the experimental procedure used to detect the elements. Hence, pure water and purified nutrient salts are utilized in studies involving mineral nutrition using hydroponics.

Q3. Explain with examples: macronutrients, micronutrients, beneficial nutrients, toxic elements and essential elements.

Ans 3. MACRONUTRIENTS — Nutrients present in more than 10mmole kg-1 of dry

matter in plant tissues are known as macronutrients. They are required in large

amounts for plant growth. Ex: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus,

Sulphur, Potassium, calcium and magnesium.

MICRONUTRIENTS - are the trace elements present in less than 10mmole kg-1 of

dry matter in plant. Example — manganese, copper, Zinc, boron, nickel.

BENEFICIAL ELEMENTS - In addition to 17essential nutrients there are some

beneficial elements required by higher plants in addition to micro and macronutrients.Ex: Sodium, Silicon, Cobalt and selenium.

TOXIC ELEMENTS are those which are required in trace amount. Their deficiency

causes diseases in plants and excess in such nutrients are toxic to plants. Ex:

Sodium, Potassium, Magnesium.

ESSENTIAL ELEMENTS - Itis an element that directly interferes in the metabolism

of the plant causing a specific deficiency symptom if not available to plants from an

external source.

Q4. Name at least five different deficiency symptoms in plants. Describe them

and correlate them with the concerned mineral deficiency.

Ans 4. Five deficiency symptoms in plants:

e Chlorosis: Loss of chlorophyll leading to the yellow colouration of the leaves. |

is caused by the deficiency of N, K, Mg, S, Fe, Mn, Zn and Mo.

Necrosis: It is the death of leaf tissue due to deficiency of Ca, Mg, Cu, K. Iti

the killing of cells expressed in the form of leaf spots, rots and blights.

Inhibition of cell division: deficiency in Mo, N, K and S causes inhibition o

Cell division. They are expressed in stunted growth.

Delay in flowering: In some plants it is caused due to low concentration of N,

and Mo.

Deformation — It is caused due to deficiency of boron. Deformation,

disorganization, discolouration of the meristematic tissue and ultimately death

of a growing plant.

Q5. If a plant shows a symptom which could develop due to deficiency of more

than one nutrient, how would you find out experimentally, the real deficient

mineral element?

Ans 5. Plants which show symptoms of multiple nutrient deficiency grown in different sets in water culture. Set 1, 2 and 3 are given three different nutrients and are grown in hydroponics by supplementing one of the different nutrients showing deficiency. If

real deficient element is supplemented then the plant will grow normally

without showing deficiency symptoms.

Q6. Why is that in certain plants deficiency symptoms appear first in younger

parts of the plant while in others they do so in mature organs?

Ans 6. Mobility of a deficient element decides the appearance of symptoms. If the

element is relatively immobile then symptoms appear in young parts and if the

deficient element is mobile, then symptoms appear in older parts of the plant.

Q7. How are the minerals absorbed by the plants?

Ans 7. The process of absorption can be established in two main phases. In the first phase, an initial rapid uptake of ions occurs passively into the ‘free space’ or ‘outer space’ of cells — the apoplast. In the second phase of uptake, the ions are taken in slowly into the symplast of the cells -‘inner space’ . The passive movement of ions into the apoplast usually takes place through ion-channels, the trans-membrane proteins that function as selective pores. The entry or exit of ions to and from the symplast requires the expenditure of metabolic energy and that is an active process.The movement of ions is usually called flux; the inward movement into the cells is influx and the outward movement, efflux.

Q8. What are the conditions necessary for fixation of atmospheric nitrogen by

Rhizobium? What is their role in N2 -fixation?

Ans 8. Following conditions are necessary for fixation of Nitrogen by

Rhizobium.Symbiotic relationship between Rhizobium and roots- necessary for the

formation of root nodules.Necessity of a reducing environment Nitrogenase enzyme — synthesizes ammonia

ATP- is required for the synthesis of ammonia NAD(P) Hz or FMNH#: is a source of reducing power

Ferredoxin — acts as an electron donor

Keto acids picks up amino group.

Nitrate as a substrate — creates reduced availability of nitrate Role of Rhizobium in N2 fixation:They fix atmospheric nitrogen in a form that can be used by plants i.e.,ammonia, using the nitrogenase enzyme.

Plant, in turn, delivers bacteria with proteins, carbohydrates and enough

oxygen so that they do not disturb the fixation process.

A plant protein -Leghaemoglobin assists in providing oxygen for respiration

process while free oxygen concentration level is still low enough to not hinder

the nitrogenase activity.

Q9. What are the steps involved in formation of a root nodule?

Ans. 9 Formation of nodules involves following steps:Rhizobia colonise the roots and get attached to epidermal and root hair cells.Bacteria invade the root hair and make it curled.Curling produces an infection thread which carries bacteria into the cortex of the root.Roots nodules are formed at the cortex of the root.

When infected thread carries the bacteria to the inner cortex, it modifies the bacteria into rod-shaped Bacteroides. It causes inner cortical and pericycle cells to undergo division. The division and growth of cortical and pericycle cells result in nodule formation.The vascular tissue continues with that of the root, then a nodule maturation is completes.

Q10. Which of the following statements are true? If false, correct them:

(a) Boron deficiency leads to stout axis.

(b) Every mineral element that is present in a cell is needed by the cell.

(d) It is very easy to establish the essentiality of micronutrients because they

are required only in trace quantities.

Ans 10. a) True

b) False- Every mineral element that is present in a cell is not needed by the cell.

c) False- Nitrogen as a nutrient is highly mobile in plants.

d) False- It is challenging to establish the essentiality of micronutrients because they are required only in trace quantities.

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INTRODUCTION:Growing plants act as integrators of all growth factors and are the products in which the grower is interested. Therefore, careful

inspection of the growing plant can help identify a specific nutrient

stress.If a plant is lacking in a particular nutrient, characteristic symptoms may appear.eficiency of a nutrient does not directly produce symptoms. Rather,

the normal plant processes are thrown out of balance, with an accumulation of certain intermediate organic compounds and a

shortage of others. This leads to the abnormal conditions.

DEFICIENCY SYMPTOMS OF ESSENTIAL ELEMENTS:

The concentration of the essential element below which plant growth is retarded is termed as critical concentration.

The element is said to be deficient when present below the critical concentration.

In the absence of any particular element, plants show certain morphological

changes, which 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.

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.The kind of deficiency symptoms shown in plants includes; chlorosis,necrosis, stunted plant growth, premature fall of leaves and buds, and

inhibition of cell division.Chlorosis is the loss of chlorophyll leading to yellowing in leaves, caused by the deficiency of elements N, K, Mg, S, Fe, Mn, Zn and Mo.

Necrosis is the death of tissue, particularly leaf tissue, is due to the

deficiency of Ca, Mg, Cu, K.

Lack or low level of N, K, S and Mo causes an inhibition of cell division.Some elements like N, S and Mo delay flowering if their concentration in plants is low.

DEFICIENCY SYMPTOMS FOR MACRONUTRIENTS:

1. NITROGEN Protein is crucial for all living organisms as it leads to growth and

development. Nitrogen is one of the significant elements in protein and

contributes to approximately 1% to 6% of plant_dry matter. The deficiency of nitrogen is seen in the overall growth and development of plants. Stems become yellow and spindly and yellow colouring of

leaves become noticeable.

2. CALCIUM Calcium is vital for cellular signaling and cell wall structure. The

deficiency of calcium impacts the young leaves and growth points of plants. New leaves become hook shaped or look distorted. Black spots may appear around mid- leaf and growth is substantially stunted.

3. MAGNESIUM Magnesium is the core element of chlorophyll and also crucial for plant

metabolism and transportation of carbohydrate along the plant body. New

growth is found to be yellow with dark spots.

4. POTASSIUM For starch formation, movement of sugar and pH stabilization, potassium is

needed. Lack of potassium leads to sudden development of necrotic tissues across the leaf margins. Eventually, the leaves will appear to be scorched. It may also curl downwards.

5. PHOSPHORUS Energy in plants in the form of Adenosine triphosphate requires

phosphorus for photosynthesis and respiration in plants. If a plant has a

deficiency of phosphorus, the small leaves may become reddish-purple,and the older leaves can become black.

6. SULPHUR Sulphur is needed for protein synthesis as it is essential for amino acids. Sulphur deficiency results in chlorosis of light greenish-yellow

pigmentation. It usually happens in young leaves.

DEFICIENCY SYMPTOMS FOR MICRONUTRIENTS

1. COPPER Poor root and stem growth can be seen. Leaves may curl, become limp or

drop.

2. BORON: Terminal buds may die along with poor growth of the plant body.

3. MANGANESE: Shoots, leaves and fruits diminish in size, and younger

leaves turn pale yellow.

4. MOLYBDENUM: Leaves become narrow and distorted with older leaves

turning yellow.

5. ZINC: Venial chlorosis and necrosis take place along with purple pigmentation in some cases.

LET US KNOW WHAT WE HAVE LEARNT!

PART: (A) VERY SHORT ANSWER TYPE QUESTIONS:-

(A) MCQS:

1. Which of the following comprise the elements that help to

complete the Lifecycle of plants?

(a) Essential elements.

(b) Non-essential elements.

(d) Micro element

2. Who had put forward the concept of essential mineral nutrients

required by plants?

(a) Carl Linnaeus.

(b) Arnon and Stout

(d) Leonhart Fuchs

3. Function of zinc is:

(a) Closing of stomata

(b) Biosynthesis of 3-IAA

(d) Oxidation of carbohydrate

4. Dark green colouration in leaves is caused due to deficiency of which mineral?

(a) Calcium

(b) Phosphorus

(d) Potassium

5. Which is not a micronutrient?

(a) Boron

(b) Zinc

(d) Molybdenum

(B) TRUE/FALSE:-

1. Boron deficiency leads to stout axis.

2. Every mineral element that is present in a cell is needed by the cell.

3. It is very easy to establish the essentiality of micronutrients because they

are required only in trace quantities.

(C) FILL IN THE BLANKS:-

1. The deficiency of magnesium result in ............chlorosis in the plants.

2. The deficiency of......causes the death of stem and root apices.

PART: (B) SHORT ANSWER TYPE QUESTIONS:-

1. What are micronutrients? Give examples

2. Mention symptoms of any four mineral deficiencies in plants

PART: (C) LONG ANSWER TYPE QUESTIONS:-

1. Give five criteria of essentiality of an element.

ANSWER KEY

PART: (A) VERY SHORT ANSWER TYPE QUESTIONS:-

a) Multiple Choice Questions:

1. (a)

2. (b)

3. (b) Zinc is required for the activity of carbonic anhydrase, auxin (Indole

acetic acid, IAA) biosynthesis

4. (b)

5. (c)

b) True/False:

1. True.

2. False. Out of all the mineral elements, only 17 are considered as essential

elements.

1 True.

c) Fill in the Blanks:

1. interveinal

2. calcium

PART: (B) SHORT ANSWER TYPE QUESTIONS:-

1. The elements that are required by the plants in fewer amounts or traces

are called micronutrients e.g. B(Boron). Mo (Molybdenum). Mn (Manganese).Cl (chlorine). These elements are present in plant tissues. They mostly act as

cofactor or activator of enzymes

2. (a) Chlorosis: Non development or loss of chlorophyll .

(b) Mottling: It is the appearance of patches of green and non-green areas

on leaves.

(d) Curling: It is caused due to unequal growth of the leaf.

PART: (C) LONG ANSWER TYPE QUESTIONS:-

1. (a) Itis indispensable for the growth of the plant.

(b) The element is directly involved in the nutrition of plants. It becomes a

component of either a structural or functional molecule. The element may additionally have a corrective effect on mineral balance and other soil conditions.

absence of the element.

(d) The element cannot be replaced by any other element.

(e) The absence or deficiency of the element produces disorders that are a

direct result of the lack or deficiency of the element.

(f) The element alone can correct the disorders produced by its absence or

deficiency.

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RECAPITULATION:NUTRITION-The sum total of processes by which a living organism receives and utilizes raw materials for building its structure and maintaining body

function is called nutrition.The chemical substances that worked as a raw material for body building and maintaining its function is termed as nutrient.

HYDROPONICS.-Solution culture is being used for raising flowers and vegetables at

home. This soilless production of plants is called hydroponics.

HYDROPONICS

CRITERIA TO KNOW ESSENTIALITY OF AN ELEMENT

1. The element is a directly involved in metabolism of plant.

2. A plant is unable to complete its vegetative and reproductive phase in

the absence of element

3. The element cannot be replaced by any other element.

4. The absence or deficiency of the element produces disorders. These

disorders are direct result of the lack or deficiency of the element.

TYPES OF ELEMENTS:

Macro elements-These are those essential elements which are present in easily detectable quantities in excess of 10m mole/kg or 1-10 mg per gram of dry matter.

Micro elements-These are those essential elements which are required by plants in small amounts less than 10m mole/kg or 1.0 mg per gram of dry matter.

Common deficiency symptoms of essential elements:

1. Chlorosis- Non development or loss of chlorophyll N, K, Mg, S, Fe, Mn,Zn, Mo.

2. Stunted growth-N, K, Ca, S, Zn, B, Mo, Cl

3. Purple coloration of shoot axis all leaves-N,P,Mg,S,Mo

4. Necrosis-death of tissue-Ca,Mg,Cu,K.

5. Premature fall of leaves and buds-P,Mg,Cu.

6. Inhibition of cell division-N,K,S,Mo

7. Dormancy of lateral buds-N,S,Mo

8. Dieback-Killing of shoot apex

9. Wilting-Loss of turgor.

10. Death of root and shoot tips-B.

11. Whiptail disease of leaves-Mo.

SYMBIOTIC NITROGEN FIXATION - Rhizobium is nitrogen fixing bacteria symbiont of papilionaceous roots. Roots have rhizobium in root nodules.

REVISION OF QUESTION ANSWERS OTHER THAN NCERT:

|. One mark question answers.

1. Name the enzyme involved in biological nitrogen fixation.

Answer- Nitrogenase

2. What is nitrification?

Answer- It is the phenomenon of conversion of ammonium nitrogen to nitrate nitrogen.

3. Which pigment is present in the root nodules of legumes?

Answer- Leghaemoglobin.

4. Name the best known symbiotic nitrogen fixing bacteria.

Answer- Rhizobium

5. How was it proved that minerals pass through xylem and not phloem?

Answer- By tracer technique.

6. What is primary deficiency?

Answer- Deficiency which is caused by critical element e.g-N, P, K.

7. Which is the most abundant element in plant body?

Answer- Oxygen.

8. What are framework elements?

Answer- Elements involved in the synthesis of cell wall and storage material,

e.g. -C, H, O.

9. Name the scientist who introduced hydroponics.

Answer- Gericke.

10. Pick out from the following list the two mineral which are not needed by

the majority of plants but very much needed by almost all animals-calcium,sodium, potassium, iron, iodine.

Answer- Sodium, iodine.

11. Define micronutrients.

Answer- Micronutrients are essential elements found in plants in small

quantities of 0.1 mg of dry matter, e.g. -Fe, Zn, B.

12. What are mineral elements?

Essential elements derived from soil are termed as mineral elements,e.g. - P, K, S.

13. What is chlorosis?

Non development or loss of chlorophyll, e.g. -N, K, Mg.

14. What is toxicity of micronutrients?

In higher doses of micronutrients become toxic. Any tissue concentration which reduces the dry weight of tissue by 10% is called toxic concentration.

15. What is a ammonification?

Ammonification is the conversion of proteins into ammonia. Proteins are first broken up into amino acids. The latter are de aminated.

ll. Two mark question answers:

1. What are the two macronutrients that usually play the most important

role in limiting plant growth, locally.

Answer- Macronutrients which become limiting in plant growth are called

critical elements. They are three in a number-N,P,K. Two of them are nitrogen

and phosphorus. Their availability in soil is generally lower than the amount

required by plants.

2. Discuss deficiency symptoms of nitrogen element.

Answer- i) Chlorosis starting from older leaves

ii) Stunted growth due to decreased Protein synthesis

iii) Smaller cells and inhibition or slow division

iv) Premature leaf fall

v) Later buds and tillering surppresed

vi) Late flowering

vii) Purple coloration of stem

viii) Reduced yield.

3. What is critical concentration?

Critical concentration is that limited concentration of the essential

elements below which growth of plant is reduced.

lll. Three marks question answers:

1. Discuss nodule formation in the root of legume.

“. ve-.. Bacteria collect over the root hairs, release nod factors that cause

curling of root hairs around the bacteria, degradation of cell wall and

formation of an infection thread and enclosing the bacteria. Infection thread

grows along with the multiplication of bacteria. It branches and its ends come

to lie opposite protoxylem points of vascular strand. The infected cortical

cells dedifferentiate and start dividing. It produces swelling or nodules. Nodule formation is stimulated by auxin produced by cortical cells and cytokinin liberated by invading bacteria.

2. What is the criteria to know essentiality of an element.

ii)it is indispensable for growth of plants.

ii)The element cannot be replaced by any other element.

iii)The element is directly involved in metabolism of plant.

iv)The absence or deficiency of the element produce disorders and element alone can correct the disorder produced by its absence or deficiency.

3. Why do farmers use leguminous crops to provide nitrogen to the soil?

Explain.Leguminous crops have nitrogen fixing bacteria in their nodules.

Leguminous plants have ability to fix atmospheric nitrogen. Leguminous

plants increase the fertility of soil so it helps in crop rotation and increase the

yield of crop.

IV. Five mark question answers:

1. Write a note on hydroponics.

Solution culture is being used for raising flowers and vegetables at home. This soilless production of plant is called hydroponics. Plants are raised in small tanks of concrete or metal. The upper covering has supports for plants. The narrow tanks are provided with nutrient solutions. A pump circulates air as well as a nutrient solution. Roots of the plants are therefore regularly provided with aerated nutrient solution. Hydroponics is useful in area having thin, infertile and dry soil. They conserve water. Additionally

hydroponics can regulate pH optimum for a particular crop, control soil borne

pathogens, avoid problems of weeding and obtain consistently better yield.

2. Write a note on absorption of minerals in plants.

Plants absorb their minerals supply from the soil through the roots.The most active areas of the root for mineral absorption are the zones of elongation and root hair. The minerals are absorbed as ions. lons are

accumulated by plants against their concentration in the soil. Isolated plant

cells, tissues or organs placed in minerals solution show two phases in mineral absorption-nitial and metabolic. In the initial phase there is a rapid uptake of ions into the outer or free space of the cells. In the metabolic phase the ions pass into inner spaces. The later comprises cytoplasm and vacuole.Entry of ions into outer space is passive absorption as no energy is required for it. Absorption of ions into in a space requirement of energy, it is therefore an active absorption.

Chapter 12 Mineral Nutrition

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Friday 5 February 2021

Chapter 12 Mineral Nutrition

Chapter 12 Mineral Nutrition

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