TS Inter 2nd Year Botany Study Material Chapter 2 Mineral Nutrition

Telangana TSBIE TS Inter 2nd Year Botany Study Material 2nd Lesson Mineral Nutrition Textbook Questions and Answers.

TS Inter 2nd Year Botany Study Material 2nd Lesson Mineral Nutrition

Very Short Answer Type Questions

Question 1.
Define hydroponics.
Answer:

1. The technique of growing plants in a specified nutrient solution is known as hydroponics.
2. Julius Von Sachs (1860) demonstrated this technique for the first time.

Question 2.
How do you categorize a particular essential element as a macro or micronutrient?
Answer:
1. Macronutients :
Elements needed in high quantities and are present is large amounts (in excess of lOmmole Kg^-1 of dry matter) in plant tissues.

2. Micronutrients :
Trace elements that are needed in very small amounts and present is less than lOmmole Kg^-1 of dry matter in plants.

Question 3.
Give two examples of essential elements that act as activators for enzymes.
Answer:
1. Mg 2⁺ is an activator of RuBp carboxylase oxygenase.
2. Zn 2⁺ is an activator of alcohol dehydrogenase.

Question 4.
Name the essential mineral elements that play an important role in photolysis of water.
Answer:
Calcium, Manganese and chlorine are the mineral elements that help is splitting of water molecules to liberate O₂ during photosynthesis.

Question 5.
Out of the 17 essential elements which elements are called non-mineral essential elements?
Answer:

1. Carbon, Hydrogen and Oxygen obtained from CO₂ and H₂O are called non – mineral essential elements.
2. These frame work elements are not absorbed from the soil as mineral nutrients. Name two amino acids in which sulphur is present.

Question 6.
Name two amino acids in which sulphur is present.
Answer:

1. Cysteine and methionine are sulphur containing amino acids.
2. They help in formation of disulphide bridges and stabilizing the protein structure.

Question 7.
When is an essential element said to be deficient?
Answer:

1. The concentration of an essential element below which plant growth is retarded is called critical concentration.
2. The element is said to be deficient when present below the critical concentration.

Question 8.
Name two elements whose symptoms of deficiency first appear in younger leaves.
Answer:

1. Sulphur and Iron.
2. Deficiency symptoms of immobile elements first appear in young leaves.

Question 9.
Explain the role of the pink colour pigment in the root nodule of legume plants. What is it called?
Answer:

1. The pink colour pigment in root nodule of legume plant is Leg-haemoglobin.
2. Enzyme nitrogenase is highly sensitive to the molecular oxygen and requires anaerobic condition. Leg haemoglobin which is an oxygen scavenger protects enzyme nitrogenase from oxygen.

Question 10.
Excess Mn in soils leads to deficiency of Ca, Mg and Fe. Justify.
Answer:

1. Manganese competes with iron and Mg for uptake and with magnesium for binding with enzymes. It also inhibits calcium translocation in the shoot apex.
2. Therefore, excess of manganese induce deficiencies of iron, magnesium and calcium.

Question 11.
What acts as a reservoir of essential elements for plants? By what process is it formed?
Answer:

1. Soil acts as a reservoir of essential elements for plants.
2. It is formed due to weathering and breakdown of rocks.

Question 12.
Which element is regarded as the 17^th essential element? Name a disease caused by its deficiency.
Answer:

1. Nickel is regarded as the 17^th essential element.
2. Its deficiency causes mouse ear in pecan.

Question 13.
Nitrogen fixation is shown by prokaryotes only. Why not by eukaryotes?
Answer:

1. Nitrogenase enzyme, which is capable of nitrogen reduction is present exclusively in prokaryotes.
2. In eukaryotes, nitrogenase enzyme is absent and so they cannot fix Nitrogen.

Question 14.
Give an example for each of the aerobic and anaerobic nitrogen fixing prokaryotes.
Answer:

1. Aerobic nitrogen fixing prokaryotes. Eg: Azotobacter, Beijernickia.
2. Anaerobic nitrogen fixing prokaryotes. Eg: Rhodospirillum.

Question 15.
Non-legume plants also form root nodules. Justify.
Answer:

1. The microbe Frankia, produces nitrogen fixing nodules on the roots of non-leguminous plants Eg: Alnus.
2. Frankia is free living in soil, but as a symbiont can fix atmospheric nitrogen.

Question 16.
Name the essential elements present in nitrogenase enzyme. What type of essential elements are they?
Answer:

1. Nitrogenase enzyme consists of 2 essential elements Molybdenum and Iron.
2. They are micronutrients.

Question 17.
Write the balanced equation of nitrogen fixation.
Answer:
N₂ + 8H⁺ + 8e^– + 16 ATP → 2NH₃ + H₂ + 16 ADP + 16 Pi

Question 18.
How many ATPs of energy is required to fix one molecule of atmospheric nitrogen by biological mode? What is the source of that energy?
Answer:

1. 16 ATP molecules, are required to fix one N₂ molecule and to produce 2 NH₃ molecules.
2. Source of that energy is obtained from the respiration of the host cells.

Question 19.
Why are amides transported through xylem?
Answer:

1. Amides contain more nitrogen than amino acids and are highly toxic to living cells.
2. Hence, they are transported to other parts of the plant through non living xylem vessels. Name any two essential elements and the deficiency diseases caused by them.

Question 20.
Name any two essential elements and the deficiency diseases caused by them.
Answer:

1. Zinc deficiency – mottled leaf in citrus.
2. Molybdenum deficiency – whip tail in cauliflower.

Short Answer Type Questions

Question 1.
“All elements that are present in a plant need not be essential for its survival.” Justify.
Answer:
Most of the elements present in the soil enter plants through roots. All the elements that are present in a plant need not be essential for its survival. The criteria for essentiality of elements are given below :

1. The element must be absolutely necessary for supporting normal growth and reproduction. In the absence of the element the plant do not complete their life cycle or set the seeds.
2. The requirement of the element must be specific and not replaceable by another element. In other words, deficiency of any one element cannot be met by supplying some other element.
3. The element must be directly involved in the metabolism of the plant.

Question 2.
Name at least five different deficiency symptoms in plants. Describe them and correlate them with the concerned mineral deficiency.
Answer:
Deficiency symptoms in plants are chlorosis, necrosis, inhibition of cell division, delay flowering.

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

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

Inhibition of cell division :
Cell division stops. It is due to the deficiency of lack or low level of N, K, S, Mo.

Delay flowering :
Flowering is delayed due to low concentration of N, S, Mo.

Mottled leaf in citrus :
It is due to deficiency of Zn,

Question 3.
Explain the steps involved in the formation of root nodule. [Mar. 2019, 18, 17, ’14]
Answer:
Steps involved in the formation of root nodule :

1. Rhizobia attracted by the sugars, amino acids etc., released by the host legume, multiply and colonise the surroundings of roots and get attached to epidermal and root hair cells.
2. The root hairs curl and the bacteria invade the root hair.
3. An infection thread is produced, carrying the bacteria into the cortex of the root.
4. Bacteria initiate nodule formation in the cortex of the root.
5. Then the bacteria released from the thread into the cortical cells of the host stimulate the host cells to divide. Thus leads to the differentiation of specialised nitrogen fixing cells.
6. The nodule thus formed establishes a direct vascular connection with the host for the exchange of nutrients.

Development of root nodules in soyabean :
(a) Rhizobium bacteria contact a susceptible root hair, divide near it. (b) Successful infection of the root hair causes it to curl, (c) Infected thread carries the bacteria to the inner cortex. The bacteria get modified into rod-shaped bacteroids and cause inner cortical and pericycle cells to divide. Division and growth of cortical and pericycle cells lead to nodule formation, (d) A mature nodule is complete with vascular tissues continuous with those of the root.

Question 4.
Some angiospermic plants have adapted to absorb molecular nitrogen from atmosphere. Explain, citing two examples.
Answer:

1. Plants cannot use atmospheric nitrogen directly. But some of the plants in association with N₂ – fixing bacteria, especially roots of legumes, can fix atmospheric nitrogen.
2. Leguminous plants (Eg : alfalfa, sweet clover, sweet pea etc.,) are associated with Rhizobium bacteria in nodular roots. Non-leguminous plants (Eg: Alnus) are associated with Frankia in nodula roots.
3. Both Rhizobium and Frankia are free – living in soil but as symbionts can fix atmospheric nitrogen.
4. Molecular nitrogen (N₂) is available abundant in air. Only prokaryotic species are capable of nitrogen fixation.
   Reduction of nitrogen to ammonia by living organisms is called biological nitrogen fixation.
5. The enzyme nitrogenase is capable of nitrogen reduction. It is present only in prokaryotes. Such microbes are called N₂ – fixers.
   

Question 5.
Write in brief how plants synthesize amino acids.
Answer:
NH₄⁺ is used to synthesize amino acids in plants. There are two main ways in which this can take place :
1) Reductive amination
2) Transamination.

1) Reductive amination :
In these processes, ammonia reacts with α-ketoglutaric acid and forms glutamic acid as indicated in the equation given below

2) Transamination :
It involves the transfer of an amino group from an amino acid to the keto group of a keto acid. Glutamic acid is the main amino acid from which the transfer of NH₂, the amino group, takes place and other amino acids are formed through transamination. The enzyme transaminase catalyses all such reactions. For example

Question 6.
What will happen if a healthy plant is supplied with excess essential elements? Explain.
Answer:

1. Excess essential element may inhibit the uptake of another element.
2. For example, the prominent symptom of manganese toxicity is the appearance of brown spots surrounded by chlorotic veins.
3. Manganese competes with iron and magnesium for uptake and with magnesium for binding with enzymes.
4. Manganese also inhibits calcium translocation in the shoot apex.
5. Therefore, excess of manganese induce deficiencies of iron, magnesium and calcium.

Question 7.
Explain in brief how plants absorb essential elements.
Answer:
1. The process of absorption of elements can be demarcated into two main phases. In the first phase, there is an initial rapid up take of ions into the free space or outer space of cells – the apoplast. It is a passive process. In the second phase of uptake, the ions are taken in slowly into the ‘inner space’ – the symplast of the cells.

2. The movement of ions into the apoplast along the concentration gradient is passive process. The movement of ions to and from the symplast against the concentration gradient requires the expenditure of metabolic energy. It is an active process.

Question 8.
Nitrogen is fixed into the soil not only by biological processes. Elaborate. [May 2014]
Answer:
Nitrogen is fixed into the soil not only by biological processes, it is also done by abiological processes.

a) In nature, due to thunders and lightening dinitrogen is converted into nitrogen oxides.
N₂ + O₂ → 2NO (nitric oxide)
2NO + O₂ → 2NO₂ (nitrogen dioxide)
2NO₂ + H₂O → HNO₂ / HNO₃ (nitrous/nitric acid)
HNO₃ + Ca/K salts → Ca/K nitrates
When nitrous/nitric acid reach the soil reacts with the alkali radical to form nitrates.

b) Industrial combustions, forest fires, automobile exhausts and power-generating stations are also the sources of atmospheric nitrogen oxides.

Long Answer Type Questions

Question 1.
Explain the nitrogen cycle, giving relevant examples. [Mar. 2020]
Answer:
The cyclic movement of nitrogen from the atmosphere to soil and from soil back into the atmosphere through plants, animals and micro-organisms is termed as nitrogen cycle. Nitrogen cycle involves five steps :

1. Nitrogen fixation
2. Nitrogen assimilation
3. Ammonification
4. Nitrification
5. Denitrification

1) Nitrogen fixation :
The process of conversion of molecular nitrogen (N₂) to ammonia or nitrogen oxides, nitrites and nitrates is termed as nitrogen – fixation. It occurs both by biological and physical method.

Biological method :
Conversion of molecular nitrogen into ammonia by prokaryotes is called biological methed.

Eg : Free – living nitrogen – fixing aerobic microbes – Azotobacter – Beijernickia.
Free living nitrogen – fixing anaerobic microbes – Rhodospirillum
Cyanobacteria (blue green algae) – Nostoc & Anabaena
Symbiotic bacteria – Rhizobium (roots of leguminous plant)
Symbiotic bacteria – Frankia (roots of non – leguminous plant)

Physical or abiological method :
In nature lightning and ultraviolet radiation provide enough energy to convert nitrogen to nitrogen oxides (NO, NO₂, NO₃). Industrial combustions, forest fires, automobile exhausts and power – generating stations are also sources of atmospheric nitrogen oxides.
N₂ + O₂ → 2NO
2NO + O₂ → 2NO₂
2NO₂ + H₂O → HNO₂ + HNO₃
HNO₃ + Ca/K salts → Ca or K nitrates

2) Nitrogen assimilation :

1. The process of absorbing nitrates, ammonia to produce organic nitrogen constitutes is called nitrogen assimilation.
2. Nitrates and ammonia formed in 1st step are absorbed by plants and converted into organic nitrogen constitute like proteins, enzymes, nucleic acid etc.
3. When plants are eaten by animats, this organic nitrogen is passed into animal body.

3) Ammonification :

1. Decomposition of organic nitrogen of dead plants and animals into ammonia is called ammonification.
2. Bacteria responsible for this are called ammonifying bacteria.

4) Nitrification :
The conversion of ammonia into nitrites and nitrates by bacteria is called nitrification. Such bacteria are called nitrifying bacteria (chemo auto trophs). It occurs in two steps.

1. Ammonia is first oxidised to nitrite by the bacteria Nitrosomonas and Nitrococcus.
   2NH₃ + 3O₂ → 2NO₂^– + 2H⁺ + 2H₂O
2. The nitrite is further oxidised to nitrate with the help of the bacterium Nitrobacter.
   2NO₂^– + O₂ → 2NO₃^–

The nitrate thus formed is absorbed by plants and is transported to the leaves. In leaves, it is reduced to form ammonia that finally forms the amine group of amino acids.

5) Denitrification :
Conversion of nitrates from soil into molecular nitrogen is called denitrification. Denitrification is done by bacteria like Pseudomonas and Thiobacillus.

Question 2.
Trace the events starting from the coming in contact of Rhizobiurri with a leguminous root till nodule formation. Add a note on the importance of leg haemoglobin.
Answer:
Various stages of nodule formation :

1. Roots of legume plant secrete sugars, amino acids etc.
2. Attracted by this, Rhizobium bacteria move to the root. It multiply and colonise the surroundings of roots and get attached to epidermal and root hair cells.
3. The root – hairs curl and the bacteria invade the root – hair.
4. An infection thread is produced, carrying the bacteria into the cortex of the root.
5. Bacteria initiate nodule formation in the cortex of the root.
6. Then the bacteria released from the thread into the cortical cells of the host stimulate the host cells to divide. Thus leads to the differentiation of specialised nitrogen fixing cells.
7. The nodule thus formed establishes a direct vascular connection with the host for exchange of nutrients.

Development of root nodules in soyabean :
(a) Rhizobium bacteria contact a susceptible root hair, divide near it. (b) Successful infection of the root hair causes it to curl, (c) Infected thread carries the bacteria to the inner cortex. The bacteria get modified into rod-shaped bacteroids and cause inner cortical and pericycle cells to divide. Division and growth of cortical and pericycle cells lead to nodule formation, (d) A mature nodule is complete with vascular tissues continuous with those of the root.

The nodule contains all the necessary biochemical components, such as the enzyme nitrogenase and leg-haemoglobin. The enzyme nitrogenase is a Mo-Fe protein and catalyses the conversion of atmospheric nitrogen to ammonia, the first stable product of nitrogen fixation.
N₂ + 8H⁺ + 8e^– + 16 ATP → 2NH₃ + H₂ + 16 ADP + 16 Pi

The enzyme nitrogenase is highly sensitive to the molecular oxygen, it requires anaerobic conditions. To protect these enzymes, the nodule contains an oxygen scavenger called leg -haemoglobin. These microbes live as aerobes under free living conditions but during nitrogen – fixing events, they adapt to anaerobic conditions, thus protecting the nitrogenase enzyme.

Intext Question Answers

Question 1.
Who should be credited for initiation of hydroponics?
Answer:
Julius von Sachs

Question 2.
Are all the essential elements required by plants mineral elements? Explain.
Answer:
Yes. Whenever the supply of an essential element becomes limited plant growth is retarded.

Question 3.
Which essential element is needed to activate the enzymes required for CO₂ fixation?
Answer:
Magnesium and Manganese.

Question 4.
Name a cation and an anion that maintain osmotic balance in cells.
Answer:
Potassium K⁺ and Chlorine Cl^–

Question 5.
Which element is required for the formation of mitotic spindle?
Answer:
Calcium

Question 6.
What is the role of sulphur in plant life?
Answer:
Sulphur is obtained in the form of sulphate SO₄^2- ions. Sulphur is present in two amino acids – cysteine and methionine and is the main constituent of several coenzymes, vitamins (thiamine, biotin, coenzyme A) and Ferredoxin. Sulphur forms disulphide bridges which help in stabilizing the protein structure.

Question 7.
Which microelement is required in more quantity than the other micronutrients ?
Answer:
Iron

Question 8.
Which element is necessary for the synthesis of the chief photosynthetic pigment without being its structural component?
Answer:
Iron and Mg

Question 9.
Which micronutrient necessary for photolysis of water is absorbed by plants in anionic form?
Answer:
Cl

Question 10.
Which enzyme is activated by the 17^th essential element?
Answer:
Nickel is the 17^th essential element which acts as an activator for Urease.

Question 11.
When is an element considered to be toxic?
Answer:
Any mineral ion concentration in tissues that reduces the dry weight of tissues by about 10 percent is considered to toxic.

Question 12.
Which element when supplied in excess leads to appearance of brown spots surrounded by chlorotic veins?
Answer:
Magnesium

Question 13.
Name an anaerobic, free living, photo-heterotrophic nitrogen fixing bacterium.
Answer:
Rhodospirillum

Question 14.
Which microorganism produces nitrogen-fixing nodules in Alnus?
Answer:
Frankia

Question 15.
When the cross section of root nodules of ground – nut plants are observed under microscope, they appear pinkish. Why?
Answer:
Due to presence of leg haemoglobin or leguminous haemoglobin.

Question 16.
Apart from the cortical cells, which other cells are stimulated to divide by the bacteroids inside the root nodules?
Answer:
Pericycle cells.

Question 17.
What is the ratio of electrons and protons required for the fixation of atmospheric mplecular nitrogen through biological mode?
Answer:
8 protons and 8 electrons i.e., 1:1 ratio.

Question 18.
What acts as oxygen scavenger in the legume-root nodule combination?
Answer:
Leg-haemoglobin

Question 19.
In what way does asparagine differ from aspartic acid?
Answer:
Asparagine is an amide found in plants as a structural part of protein. It is formed from aspartic acid by additional of another amino group.

Question 20.
Through which tissue the amino acids are transported inside the plant body?
Answer:
Amino acids are transported to other parts of the plant body via xylem vessels.

Question 21.
Plants like the Pitcher and Venus fly trap have special nutritional adaptations. Name the essential element and its source for which they show such adaptations.
Answer:

1. N₂ (Nitrogen)
2. Nitrogen is absorbed from the insect body.