Topic: Plant Tissue Culture; Subtopic: Totipotency and Micropropagation
Keyword Definitions:
Totipotency: The ability of a single plant cell to regenerate into a complete plant under appropriate conditions.
Micropropagation: Rapid multiplication of plants using tissue culture techniques from a small explant.
Differentiation: The process by which unspecialized cells become specialized into specific cell types.
Somatic Hybridization: Fusion of two somatic cells from different species to create a hybrid plant.
Plant Tissue Culture: The in vitro cultivation of plant cells, tissues, or organs under sterile conditions on a nutrient medium.
Lead Question – 2024
The capacity to generate a whole plant from any cell of the plant is called:
(1) Micropropagation
(2) Differentiation
(3) Somatic hybridization
(4) Totipotency
Explanation: Totipotency refers to the ability of a single plant cell to develop into a complete plant under suitable conditions. This property is fundamental to plant tissue culture and enables micropropagation. Differentiation, micropropagation, and somatic hybridization are related techniques, but the intrinsic cellular capacity to regenerate a whole plant is specifically called totipotency. (Answer: 4)
1. Which hormone is commonly used to induce shoot formation in plant tissue culture?
(1) Auxin
(2) Cytokinin
(3) Gibberellin
(4) Abscisic acid
Explanation: Cytokinins are plant hormones that promote cell division and shoot formation in tissue culture. They are used to stimulate multiple shoot regeneration from explants. Auxins usually promote root formation, gibberellins stimulate elongation, and abscisic acid regulates dormancy. Therefore, for shoot induction, cytokinins are essential. (Answer: 2)
2. Micropropagation is advantageous because it:
(1) Produces genetically identical plants
(2) Requires seeds for propagation
(3) Reduces plant growth rate
(4) Produces heterozygous offspring
Explanation: Micropropagation allows rapid clonal multiplication of plants, producing genetically identical offspring. It does not rely on seeds, thus bypassing seed dormancy issues. This method enhances uniformity and maintains desirable traits in large-scale production. It is widely applied for horticultural, medicinal, and ornamental plants. (Answer: 1)
3. In somatic hybridization, the primary technique involves:
(1) Pollen transfer
(2) Fusion of somatic cells
(3) Seed germination
(4) Grafting
Explanation: Somatic hybridization involves fusion of two somatic (non-gamete) cells from different plant species using protoplast fusion techniques. This produces hybrid cells that can regenerate into hybrid plants. Pollen transfer, seed germination, and grafting are conventional methods, not involving somatic cell fusion. (Answer: 2)
4. Which of the following is NOT a requirement for successful plant tissue culture?
(1) Sterile conditions
(2) Nutrient medium
(3) Light, temperature, and humidity control
(4) Soil for rooting
Explanation: Plant tissue culture is performed in vitro on artificial nutrient media under sterile conditions. Light, temperature, and humidity are controlled. Soil is not required for initial growth; rooting can be induced in vitro or transferred to soil later. Thus, soil is not essential in the tissue culture process. (Answer: 4)
5. Which type of explant is commonly used for callus induction?
(1) Leaf segment
(2) Root tip
(3) Seed
(4) Stem node
Explanation: Leaf segments are commonly used as explants for callus induction in plant tissue culture. They respond well to auxin-rich media to form an undifferentiated callus, which can later differentiate into shoots or roots. Roots, seeds, and stem nodes are also used, but leaves are preferred for uniform callus formation. (Answer: 1)
6. In tissue culture, auxins primarily promote:
(1) Shoot formation
(2) Root formation
(3) Flower formation
(4) Somatic hybridization
Explanation: Auxins are plant hormones that stimulate cell elongation and root initiation in tissue culture. They are essential for rooting of microshoots during plant regeneration. Cytokinins are used for shoot formation. Flower formation is regulated by gibberellins, and somatic hybridization is a separate technique. (Answer: 2)
7. Assertion-Reason Type:
Assertion (A): Totipotency is a key concept in plant biotechnology.
Reason (R): Every plant cell can differentiate into specialized tissues under normal conditions.
(1) Both A and R are true and R is correct explanation of A
(2) Both A and R are true but R is not correct explanation of A
(3) A is true, R is false
(4) A is false, R is true
Explanation: Totipotency allows a single plant cell to generate a whole plant under suitable conditions, making it crucial in biotechnology. However, under normal conditions, not every plant cell differentiates spontaneously into all tissues. Therefore, Assertion is true, but Reason is false. (Answer: 3)
8. Matching Type Question:
Match the terms with definitions:
A. Micropropagation – (i) Clonal multiplication
B. Totipotency – (ii) Cell can form whole plant
C. Somatic hybridization – (iii) Fusion of somatic cells
D. Callus – (iv) Undifferentiated tissue
Options:
(1) A–i, B–ii, C–iii, D–iv
(2) A–ii, B–i, C–iv, D–iii
(3) A–iv, B–iii, C–ii, D–i
(4) A–iii, B–iv, C–i, D–ii
Explanation: Micropropagation refers to clonal multiplication, totipotency is the ability of a cell to form a whole plant, somatic hybridization involves fusion of somatic cells, and callus is undifferentiated tissue. Therefore, correct matching is A–i, B–ii, C–iii, D–iv. (Answer: 1)
9. Fill in the Blanks:
The undifferentiated mass of plant cells formed in vitro is called __________.
(1) Explant
(2) Callus
(3) Protoplast
(4) Meristem
Explanation: Callus is an undifferentiated mass of plant cells produced in vitro, typically induced from explants using auxins and cytokinins. It serves as the starting material for regeneration of shoots and roots in tissue culture techniques. Explants are tissue sources, protoplasts are cells without walls, and meristems are naturally dividing tissues. (Answer: 2)
10. Choose the Correct Statements:
Statement I: Micropropagation helps in producing disease-free plants.
Statement II: Totipotency allows regeneration of whole plants from single cells.
(1) Both statements are true
(2) Both statements are false
(3) Statement I is true, Statement II is false
(4) Statement I is false, Statement II is true
Explanation: Micropropagation is widely used to produce large numbers of disease-free plants due to aseptic culture conditions. Totipotency is the intrinsic ability of plant cells to regenerate into a whole plant, which forms the basis of tissue culture and regeneration techniques. Hence, both statements are correct. (Answer: 1)
Keyword Definitions:
Tissue Culture: Technique of growing plant cells, tissues, or organs in a nutrient medium under sterile conditions.
Leaf Mesophyll Cells: Parenchymatous cells present in the middle layer of leaf, responsible for photosynthesis.
Callus: Mass of undifferentiated plant cells produced in vitro from explants.
Dedifferentiation: Process where specialized cells revert to a less specialized, meristematic state.
Differentiation: Development of cells into specialized types performing specific functions.
Development: Progressive process of growth and differentiation leading to mature structure formation.
Senescence: Aging process of cells resulting in loss of function and eventual death.
Culture Medium: Nutrient solution or solid medium that supports in vitro growth of cells or tissues.
Explant: Tissue taken from a plant to initiate culture.
Meristematic Cells: Undifferentiated cells capable of division and giving rise to specialized tissues.
In Vitro: Experimental process carried out outside the organism in controlled environment.
Lead Question - 2023:
In tissue culture experiments, leaf mesophyll cells are put in a culture medium to form callus. This phenomenon may be called as:
(1) Development
(2) Senescence
(3) Differentiation
(4) Dedifferentiation
Answer & Explanation: (4) Dedifferentiation. In tissue culture, leaf mesophyll cells, which are normally differentiated for photosynthesis, lose their specialized characteristics when placed in a suitable nutrient medium. These cells revert to a meristematic state and divide to form a callus. This reversal from a specialized to an unspecialized state is called dedifferentiation. The callus is undifferentiated tissue capable of further growth and regeneration into complete plantlets under appropriate hormonal conditions. This process demonstrates cellular plasticity and is a key concept in plant biotechnology for cloning, genetic engineering, and regeneration studies. Dedifferentiation is distinct from differentiation, development, or senescence.
1. Which hormone combination is commonly used to induce callus formation?
(1) Auxin + Cytokinin
(2) Gibberellin + Ethylene
(3) Abscisic acid + Auxin
(4) Cytokinin + Gibberellin
Explanation: Auxin and cytokinin in proper ratios induce dedifferentiation and callus formation. Correct answer is (1).
2. Callus tissue is primarily composed of:
(1) Differentiated cells
(2) Meristematic undifferentiated cells
(3) Vascular tissue
(4) Epidermal cells
Explanation: Callus consists of undifferentiated meristematic cells capable of division. Correct answer is (2).
3. Leaf mesophyll cells in culture lose:
(1) Their photosynthetic pigments
(2) Cell wall
(3) Genetic material
(4) Cytoplasm
Explanation: Dedifferentiation involves loss of specialized function like photosynthesis. Correct answer is (1).
4. Explant in plant tissue culture refers to:
(1) Nutrient medium
(2) Tissue taken from plant for culture
(3) Callus
(4) Hormone
Explanation: Explant is the tissue excised from a plant to initiate in vitro culture. Correct answer is (2).
5. Which process allows callus to regenerate into whole plants?
(1) Dedifferentiation
(2) Somatic embryogenesis
(3) Senescence
(4) Differentiation
Explanation: Callus can undergo somatic embryogenesis to regenerate into complete plants. Correct answer is (2).
6. Callus formation is a type of:
(1) Differentiation
(2) Dedifferentiation
(3) Senescence
(4) Apoptosis
Explanation: Cells revert to unspecialized meristematic state forming callus, representing dedifferentiation. Correct answer is (2).
Assertion-Reason Type Question
7. Assertion (A): Leaf explants can form callus in vitro.
Reason (R): Mesophyll cells dedifferentiate and divide in culture medium.
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true
Explanation: Dedifferentiation allows mesophyll cells to divide forming callus; both statements are correct and R explains A. Correct answer is (1).
Matching Type Question
8. Match the term with description:
A. Dedifferentiation – (i) Specialized cell function
B. Callus – (ii) Undifferentiated mass
C. Differentiation – (iii) Conversion to specialized cells
D. Explant – (iv) Tissue used for culture
(1) A-(ii), B-(ii), C-(iii), D-(iv)
(2) A-(iii), B-(iv), C-(ii), D-(i)
(3) A-(ii), B-(iii), C-(i), D-(iv)
(4) A-(iv), B-(ii), C-(iii), D-(i)
Explanation: Correct matches: Dedifferentiation-undifferentiated; Callus-mass; Differentiation-specialized cells; Explant-tissue source. Correct answer is (1).
Fill in the Blanks Question
9. The process where mature mesophyll cells revert to meristematic state is called ______.
(1) Differentiation
(2) Dedifferentiation
(3) Senescence
(4) Development
Explanation: Reversion of specialized cells to meristematic state is dedifferentiation. Correct answer is (2).
Choose the Correct Statements Question
10. Statement I: Callus is undifferentiated tissue.
Statement II: Dedifferentiation is necessary for callus formation.
(1) I true, II false
(2) I false, II true
(3) Both true
(4) Both false
Explanation: Callus consists of undifferentiated cells and dedifferentiation allows its formation. Both statements are correct. Correct answer is (3).
Topic: Plant Tissue Culture; Subtopic: Cell Differentiation and Dedifferentiation
Keyword Definitions:
• Parenchyma cells: Fundamental plant cells with thin walls involved in storage, photosynthesis, and regeneration.
• Dedifferentiation: Process where mature cells lose specialized features and regain the ability to divide.
• Redifferentiation: Process by which dedifferentiated cells regain specialized functions.
• Differentiation: Development of specialized cell types from meristematic cells.
• Secondary growth: Increase in thickness or girth of stems and roots via cambium activity.
• Plant tissue culture: Technique of growing plant cells or tissues in an artificial nutrient medium under sterile conditions.
• Mitosis: Cell division resulting in two genetically identical daughter cells.
• Meristem: Region of actively dividing plant cells.
• Totipotency: Ability of a single cell to regenerate into a whole plant.
• Callus: Mass of undifferentiated plant cells formed during tissue culture.
• Phenomenon: Observable event or process in biological systems.
Lead Question - 2022 (Ganganagar)
The phenomenon by which the undividing parenchyma cells start to divide mitotically during plant tissue culture is called as:
1. Differentiation
2. Dedifferentiation
3. Redifferentiation
4. Secondary growth
Explanation: Dedifferentiation is the process in which mature parenchyma cells lose their specialized features and regain the capacity to divide. This is a critical step in plant tissue culture as it leads to the formation of callus from mature tissues. Dedifferentiated cells are totipotent, enabling regeneration of whole plants under suitable conditions. Hence, the correct answer is 2. Dedifferentiation ensures that cells can undergo mitosis, eventually leading to redifferentiation for organ formation or complete plant development in vitro. This process is central to plant biotechnology and micropropagation strategies.
1. Single Correct Answer MCQ:
Which plant hormone primarily induces dedifferentiation in tissue culture?
a) Auxin
b) Gibberellin
c) Cytokinin
d) Ethylene
Explanation: Auxins, especially 2,4-D, play a crucial role in inducing dedifferentiation by stimulating cell division in mature plant tissues. They promote callus formation in culture by reactivating the cell cycle in parenchyma cells. Cytokinins balance auxins for shoot regeneration, while gibberellins and ethylene have secondary roles. The answer is a) Auxin.
2. Single Correct Answer MCQ:
The mass of undifferentiated cells formed after dedifferentiation is called:
a) Meristem
b) Callus
c) Cortex
d) Cambium
Explanation: Callus is a proliferating mass of undifferentiated parenchyma cells formed during tissue culture. It originates from dedifferentiated cells and can be induced to redifferentiate into shoots or roots under hormonal control. Meristem and cambium are naturally dividing tissues, while cortex is a differentiated storage tissue. Correct answer is b) Callus.
3. Single Correct Answer MCQ:
Totipotency refers to:
a) Ability of cells to divide
b) Ability to regenerate a whole plant from a single cell
c) Differentiation of cells
d) Secondary growth
Explanation: Totipotency is the capacity of a single plant cell to regenerate into an entire plant. Dedifferentiated parenchyma cells in tissue culture exhibit totipotency, enabling micropropagation and genetic engineering. Differentiation is the process of acquiring specialized features. Secondary growth increases thickness. Correct answer is b) Ability to regenerate a whole plant from a single cell.
4. Single Correct Answer MCQ:
Which medium component is essential for in vitro plant tissue culture?
a) Agar
b) Sodium chloride
c) Alcohol
d) Calcium carbonate
Explanation: Agar is used as a gelling agent to provide a solid support in tissue culture media. It allows cells to grow in place and absorb nutrients. Sodium chloride and alcohol are not used, while calcium carbonate can adjust pH but is not essential. Correct answer is a) Agar.
5. Single Correct Answer MCQ:
Redifferentiation in tissue culture leads to:
a) Callus formation
b) Organogenesis
c) Dedifferentiation
d) Secondary growth
Explanation: Redifferentiation is the process by which dedifferentiated cells regain specialization to form organs like roots or shoots in vitro. This is the key step in plant regeneration after callus formation. Dedifferentiation precedes this stage. Secondary growth is unrelated. Correct answer is b) Organogenesis.
6. Single Correct Answer MCQ:
Which plant tissue naturally retains meristematic activity throughout life?
a) Parenchyma
b) Collenchyma
c) Meristem
d) Xylem
Explanation: Meristematic tissue consists of undifferentiated, actively dividing cells responsible for primary and secondary growth. Parenchyma can dedifferentiate, but meristems naturally remain mitotically active. Collenchyma and xylem are differentiated tissues. Correct answer is c) Meristem.
7. Assertion-Reason MCQ:
Assertion (A): Dedifferentiated cells are totipotent.
Reason (R): Totipotent cells can regenerate into a complete plant.
a) Both A and R are true, R explains A
b) Both A and R are true, R does not explain A
c) A is true, R is false
d) A is false, R is true
Explanation: Dedifferentiated cells regain the ability to divide and exhibit totipotency, allowing them to regenerate into an entire plant. This totipotency is essential for successful tissue culture and micropropagation. Both the assertion and reason are correct, and the reason properly explains the assertion. Correct answer is a) Both A and R are true, R explains A.
8. Matching Type MCQ:
Match the following:
Column I
A) 2,4-D
B) BAP
C) Callus
D) Auxin
Column II
1) Shoot regeneration
2) Cytokinin
3) Cell proliferation
4) Indole-3-acetic acid
Choices:
A-__ B-__ C-__ D-__
Explanation: 2,4-D induces callus formation (A-3). BAP is a cytokinin used for shoot regeneration (B-2). Callus is a mass of undifferentiated cells (C-3). Auxin like IAA promotes cell division and elongation (D-4). Proper matching ensures successful tissue culture outcomes. Correct matches: A-3, B-1, C-3, D-4.
9. Fill in the Blanks / Completion MCQ:
The first step in plant tissue culture involves __________ of mature cells.
a) Differentiation
b) Dedifferentiation
c) Redifferentiation
d) Secondary growth
Explanation: Dedifferentiation is the initial step in plant tissue culture where mature cells lose their specialized state and regain the ability to divide. This allows callus formation, which can later undergo redifferentiation for organ development. Differentiation and secondary growth are unrelated in initial tissue culture steps. Correct answer is b) Dedifferentiation.
10. Choose the correct statements MCQ (Statement I & II):
Statement I: Dedifferentiation leads to callus formation.
Statement II: Callus cells can be redifferentiated into organs under hormonal control.
a) Both I and II are correct
b) Only I is correct
c) Only II is correct
d) Both are incorrect
Explanation: Dedifferentiation of mature plant cells results in callus formation (Statement I), and such callus cells are totipotent and can be induced to redifferentiate into shoots or roots under appropriate hormonal treatment (Statement II). Both statements are true and describe sequential steps in plant tissue culture. Correct answer is a) Both I and II are correct.
Topic: Plant Growth Regulators and Tissue Culture
Subtopic: Hormonal Regulation of Differentiation
Keyword Definitions:
• Auxin: Plant hormone promoting cell elongation and root initiation.
• Cytokinin: Plant hormone promoting cell division and shoot formation.
• Gibberellin: Plant hormone that stimulates stem elongation and seed germination.
• Abscisic acid: Plant hormone involved in dormancy and stress responses.
Lead Question - 2016 (Phase 2):
You are given a tissue with potential for differentiation in an artificial culture. Which of the following pairs of hormones would you add to the medium to secure shoots as well as roots?
(1) Gibberellin and abscisic acid
(2) IAA and gibberellin
(3) Auxin and cytokinin
(4) Auxin and abscisic acid
Explanation: In plant tissue culture, a combination of auxin and cytokinin regulates organogenesis. Auxin promotes root formation while cytokinin promotes shoot development. Their ratio in the medium determines the balance between shoots and roots. Correct answer is (3) Auxin and cytokinin, a key concept for NEET UG plant biotechnology.
1. Single Correct Answer MCQ:
Which hormone primarily promotes shoot formation in tissue culture?
(1) Auxin
(2) Cytokinin
(3) Gibberellin
(4) Abscisic acid
Explanation: Cytokinin promotes cell division and shoot formation in plant tissue culture. The ratio of cytokinin to auxin determines whether shoots or roots develop. Auxin primarily promotes roots. Correct answer: (2) Cytokinin, fundamental for NEET UG tissue culture studies.
2. Single Correct Answer MCQ:
Auxin in tissue culture mainly induces
(1) Shoot elongation
(2) Root initiation
(3) Seed germination
(4) Dormancy
Explanation: Auxin stimulates cell elongation and differentiation, particularly root initiation in tissue culture. Its interaction with cytokinin controls organogenesis. The correct answer is (2) Root initiation, important for NEET UG plant growth regulator understanding.
3. Single Correct Answer MCQ:
Gibberellins in tissue culture are used to
(1) Induce roots
(2) Promote stem elongation
(3) Inhibit shoot growth
(4) Prevent callus formation
Explanation: Gibberellins stimulate stem elongation and mobilize stored nutrients in seed germination. They do not induce roots or shoots directly in tissue culture. Correct answer: (2) Promote stem elongation, relevant for NEET UG plant physiology.
4. Single Correct Answer MCQ:
Abscisic acid primarily functions to
(1) Promote shoot growth
(2) Induce dormancy
(3) Stimulate root elongation
(4) Enhance cytokinin activity
Explanation: Abscisic acid regulates dormancy, stress responses, and inhibits growth under adverse conditions. It is not used for organogenesis in tissue culture. Correct answer: (2) Induce dormancy, essential for NEET UG hormone function knowledge.
5. Single Correct Answer MCQ (Clinical-type):
A plant tissue culture lab fails to produce roots. Which hormone should be increased?
(1) Cytokinin
(2) Auxin
(3) Gibberellin
(4) Abscisic acid
Explanation: Increasing auxin concentration promotes root formation in tissue culture. Cytokinin promotes shoots, while gibberellin and abscisic acid are not primarily involved in root initiation. Correct answer: (2) Auxin, crucial for NEET UG plant tissue culture troubleshooting.
6. Single Correct Answer MCQ:
In callus culture, which hormone combination favors organogenesis?
(1) High auxin, low cytokinin
(2) High cytokinin, low auxin
(3) Equal auxin and cytokinin
(4) Auxin and abscisic acid
Explanation: Equal or balanced concentrations of auxin and cytokinin promote organogenesis in callus culture, allowing differentiation into shoots and roots. The correct answer is (3) Equal auxin and cytokinin, vital for NEET UG plant biotechnology concepts.
7. Assertion-Reason MCQ:
Assertion (A): Cytokinin promotes shoot formation.
Reason (R): Cytokinin stimulates cell division in meristematic tissues.
(1) Both A and R are true and R is correct explanation of A
(2) Both A and R are true but R is not correct explanation of A
(3) A is true but R is false
(4) A is false but R is true
Explanation: Both assertion and reason are true, and reason correctly explains the assertion. Cytokinin induces shoot formation by promoting cell division in meristematic tissues. Correct answer: (1) Both A and R are true and R is correct explanation of A.
8. Matching Type MCQ:
Match the hormone with its primary role:
A. Auxin
B. Cytokinin
C. Gibberellin
D. Abscisic acid
1. Root initiation
2. Shoot formation
3. Stem elongation
4. Dormancy induction
Options:
(1) A-1, B-2, C-3, D-4
(2) A-2, B-1, C-3, D-4
(3) A-1, B-3, C-2, D-4
(4) A-4, B-2, C-3, D-1
Explanation: The correct match is A-1 (Auxin-root initiation), B-2 (Cytokinin-shoot formation), C-3 (Gibberellin-stem elongation), D-4 (Abscisic acid-dormancy induction). Correct answer: (1) A-1, B-2, C-3, D-4, key for NEET UG plant hormone functions.
9. Fill in the Blanks MCQ:
For inducing both shoots and roots in tissue culture, ______ and ______ are required.
(1) Auxin and gibberellin
(2) Auxin and cytokinin
(3) Gibberellin and abscisic acid
(4) Auxin and abscisic acid
Explanation: Balanced concentrations of auxin and cytokinin in culture medium enable simultaneous development of shoots and roots from totipotent tissue. Correct answer: (2) Auxin and cytokinin, essential knowledge for NEET UG tissue culture practices.
10. Choose the Correct Statements MCQ:
Select correct statements regarding plant tissue culture hormones:
(1) Auxin promotes root development
(2) Cytokinin promotes shoot development
(3) Gibberellin induces organogenesis
(4) Balanced auxin and cytokinin promotes both shoots and roots
Options:
(1) 1, 2, and 4 only
(2) 1 and 3 only
(3) 2 and 3 only
(4) All statements are correct
Explanation: Statements 1, 2, and 4 are correct. Auxin induces roots, cytokinin induces shoots, and balanced auxin and cytokinin promotes both shoots and roots. Gibberellin does not induce organogenesis. Correct answer: (1) 1, 2, and 4 only.