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.