Question:
Zinc is responsible for the biosynthesis of which plant auxin ?
Zinc is responsible for the biosynthesis of which plant auxin ?
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Zinc deficiency limits tryptophan production, which in turn reduces IAA synthesis.
This biochemical link is why zinc deficiency leads to "little leaf" and "rosetting" in plants.
This biochemical link is why zinc deficiency leads to "little leaf" and "rosetting" in plants.
Updated On: Aug 7, 2026
- NAA
- 2,4-D
- IBA
- IAA
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The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
Auxins are plant hormones that regulate key growth processes, including cell elongation, apical dominance, and root development.
Indole-3-acetic acid (IAA) is the primary naturally occurring auxin in plants.
Step 2: Detailed Explanation:
The synthesis of the natural auxin IAA occurs mainly through a tryptophan-dependent biochemical pathway.
Tryptophan is an essential amino acid that serves as the precursor for IAA.
Zinc ($\text{Zn}$) is an essential micronutrient that acts as an activator and cofactor for enzymes involved in the synthesis of tryptophan.
If a plant is deficient in zinc, tryptophan synthesis is blocked, which prevents the production of IAA.
This hormone deficiency leads to reduced cell elongation, resulting in classic symptoms like shortened internodes ("rosetting") and smaller leaves ("little leaf").
Other options like NAA and 2,4-D are synthetic growth regulators and are not synthesized naturally by plants.
Step 3: Final Answer:
Zinc is required for the biosynthesis of the plant auxin IAA (Indole-3-acetic acid), which corresponds to Option (D).
Auxins are plant hormones that regulate key growth processes, including cell elongation, apical dominance, and root development.
Indole-3-acetic acid (IAA) is the primary naturally occurring auxin in plants.
Step 2: Detailed Explanation:
The synthesis of the natural auxin IAA occurs mainly through a tryptophan-dependent biochemical pathway.
Tryptophan is an essential amino acid that serves as the precursor for IAA.
Zinc ($\text{Zn}$) is an essential micronutrient that acts as an activator and cofactor for enzymes involved in the synthesis of tryptophan.
If a plant is deficient in zinc, tryptophan synthesis is blocked, which prevents the production of IAA.
This hormone deficiency leads to reduced cell elongation, resulting in classic symptoms like shortened internodes ("rosetting") and smaller leaves ("little leaf").
Other options like NAA and 2,4-D are synthetic growth regulators and are not synthesized naturally by plants.
Step 3: Final Answer:
Zinc is required for the biosynthesis of the plant auxin IAA (Indole-3-acetic acid), which corresponds to Option (D).
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