Question:
Identify the "Growth Retardants" used in crop plants:
A. Maleic Hydrazide
B. Chloromequat Chloride
C. Paclobutrazole
D. Triiodobenzoic acid
Choose the correct answer from the options given below:
Identify the "Growth Retardants" used in crop plants:
A. Maleic Hydrazide
B. Chloromequat Chloride
C. Paclobutrazole
D. Triiodobenzoic acid
Choose the correct answer from the options given below:
A. Maleic Hydrazide
B. Chloromequat Chloride
C. Paclobutrazole
D. Triiodobenzoic acid
Choose the correct answer from the options given below:
Show Hint
Retardants = Slow down (usually anti-GAs). Inhibitors = Stop specific processes (MH, ABA). TIBA = Anti-auxin transport.
Updated On: Aug 21, 2026
- A, C and D only
- A, B and D only
- B, C and D only
- B and C only
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Verified By Collegedunia
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
Growth Retardants are a specific class of Plant Growth Regulators that slow down the rate of stem elongation and cell division without causing malformations. They often work by inhibiting Gibberellin (GA) biosynthesis. These are distinct from "Inhibitors" like ABA or metabolic poisons.
Step 2: Detailed Explanation:
1. Chloromequat Chloride (CCC/Cycocel) (B): A classic GA biosynthesis inhibitor (it blocks the cyclization of geranylgeranyl pyrophosphate). It is widely used to prevent lodging in wheat and for making ornamental plants bushy. It is a quintessential retardant.
2. Paclobutrazole (C): A triazole growth retardant. It inhibits the oxidation of ent-kaurene to ent-kaurenoic acid in the GA pathway. It is used extensively in fruit crops (like mango) to control vigor and induce flowering. It is a true growth retardant.
3. Maleic Hydrazide (MH) (A): This is often classified as a Growth Inhibitor because it acts as a uracil antagonist, inhibiting DNA synthesis and cell division throughout the plant. It is used to prevent sprouting in onions and potatoes. While it restricts growth, it is technically an inhibitor rather than a retardant in many formal classifications.
4. Triiodobenzoic acid (TIBA) (D): This is an Auxin Transport Inhibitor. It blocks the polar transport of IAA. While it reduces growth, it is categorized as a transport inhibitor.
The most definitive "Growth Retardants" in the biological sense are the GA inhibitors B and C.
Step 3: Final Answer:
Chloromequat Chloride and Paclobutrazole are identified as the primary growth retardants.
Growth Retardants are a specific class of Plant Growth Regulators that slow down the rate of stem elongation and cell division without causing malformations. They often work by inhibiting Gibberellin (GA) biosynthesis. These are distinct from "Inhibitors" like ABA or metabolic poisons.
Step 2: Detailed Explanation:
1. Chloromequat Chloride (CCC/Cycocel) (B): A classic GA biosynthesis inhibitor (it blocks the cyclization of geranylgeranyl pyrophosphate). It is widely used to prevent lodging in wheat and for making ornamental plants bushy. It is a quintessential retardant.
2. Paclobutrazole (C): A triazole growth retardant. It inhibits the oxidation of ent-kaurene to ent-kaurenoic acid in the GA pathway. It is used extensively in fruit crops (like mango) to control vigor and induce flowering. It is a true growth retardant.
3. Maleic Hydrazide (MH) (A): This is often classified as a Growth Inhibitor because it acts as a uracil antagonist, inhibiting DNA synthesis and cell division throughout the plant. It is used to prevent sprouting in onions and potatoes. While it restricts growth, it is technically an inhibitor rather than a retardant in many formal classifications.
4. Triiodobenzoic acid (TIBA) (D): This is an Auxin Transport Inhibitor. It blocks the polar transport of IAA. While it reduces growth, it is categorized as a transport inhibitor.
The most definitive "Growth Retardants" in the biological sense are the GA inhibitors B and C.
Step 3: Final Answer:
Chloromequat Chloride and Paclobutrazole are identified as the primary growth retardants.
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