Question:
Which of the following hormone deficiency causes dwarfism in plant?
Which of the following hormone deficiency causes dwarfism in plant?
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Classic genetic dwarfism in plants is caused by a deficiency in Gibberellins. This dwarfism can be overcome by applying exogenous Gibberellic Acid (\(\text{GA}_3\)), which stimulates rapid internodal elongation.
Updated On: Aug 5, 2026
- Auxin
- Gibberellin
- Brassinosteroid
- Ethylene
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The Correct Option is B
Solution and Explanation
Step 1: Understanding the Concept:
Phytohormones (plant hormones) are chemical messengers that regulate plant growth, development, and physiological responses.
A deficiency in these hormones, often caused by genetic mutations, can lead to distinct physical abnormalities.
Step 2: Detailed Explanation:
Let us analyze how each hormone affects plant height:
- Auxin: Promotes apical dominance, cell elongation, and root initiation, but its deficiency does not cause classic dwarfism.
- Gibberellins (GAs): These hormones play a key role in stimulating stem elongation by promoting cell division and cell elongation in the internodes.
- A genetic mutation that blocks the synthesis of active gibberellins (or prevents the plant from responding to them) results in a severe reduction in internode length, causing genetic dwarfism.
- This dwarf phenotype can be reversed by applying external gibberellic acid (GA), which stimulates rapid stem elongation and restores the plant to its normal, tall height.
- This discovery was crucial to the Green Revolution, where semi-dwarf wheat and rice varieties were bred with altered gibberellin pathways to make them lodging-resistant and highly responsive to fertilizers.
- Brassinosteroids: Also promote stem elongation, but classic genetic dwarfism studied in agricultural crops is primarily associated with gibberellin pathways.
- Ethylene: A gaseous hormone that inhibits stem elongation and promotes ripening and abscission.
Step 3: Final Answer:
The correct option is (B).
Phytohormones (plant hormones) are chemical messengers that regulate plant growth, development, and physiological responses.
A deficiency in these hormones, often caused by genetic mutations, can lead to distinct physical abnormalities.
Step 2: Detailed Explanation:
Let us analyze how each hormone affects plant height:
- Auxin: Promotes apical dominance, cell elongation, and root initiation, but its deficiency does not cause classic dwarfism.
- Gibberellins (GAs): These hormones play a key role in stimulating stem elongation by promoting cell division and cell elongation in the internodes.
- A genetic mutation that blocks the synthesis of active gibberellins (or prevents the plant from responding to them) results in a severe reduction in internode length, causing genetic dwarfism.
- This dwarf phenotype can be reversed by applying external gibberellic acid (GA), which stimulates rapid stem elongation and restores the plant to its normal, tall height.
- This discovery was crucial to the Green Revolution, where semi-dwarf wheat and rice varieties were bred with altered gibberellin pathways to make them lodging-resistant and highly responsive to fertilizers.
- Brassinosteroids: Also promote stem elongation, but classic genetic dwarfism studied in agricultural crops is primarily associated with gibberellin pathways.
- Ethylene: A gaseous hormone that inhibits stem elongation and promotes ripening and abscission.
Step 3: Final Answer:
The correct option is (B).
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