The Question is from neet-zoology strategies-for-enhancement-in-food-production tissue-culture, and it was created by the author K SUNKANNA

Question

A researcher is attempting to induce differentiation in a callus culture of a rare medicinal plant. Which of the following combinations of plant growth regulators is LEAST likely to promote shoot formation?

K SUNKANNA · Accepted Answer

## CORE INFORMATION
✓ **Answer**: D
## CONCEPT FRAMEWORK
	**Primary Concept**: Plant Growth Regulators (PGRs) and their roles in plant tissue culture.
	**Related Topics**: Auxins, Cytokinins, Gibberellins, Abscisic Acid.
	**Prerequisites**: Understanding of the roles of different PGRs in promoting shoot formation versus root formation in plant tissue culture.
## SOLUTION PATHWAY
**Given Information**:
		1. High Auxin and Low Cytokinin (Option A)
		2. Low Auxin and High Cytokinin (Option B)
		3. High Gibberellin and Low Abscisic Acid (Option C)
		4. High 2,4-D and High Kinetin (Option D)
**Method & Steps**:
	1. Identify the role of Auxins and Cytokinins in shoot formation.
		Reasoning: Auxins generally promote root formation, while Cytokinins promote shoot formation. A high ratio of Cytokinins to Auxins is typically favorable for shoot induction.
		Formula/Rule: The effectiveness of PGRs can often be summarized by the Auxin/Cytokinin ratio.
	2. Assess the combinations provided.
		Working: 
		- Option A: High Auxin and Low Cytokinin would promote root formation more than shoot formation. 
		- Option B: Low Auxin and High Cytokinin is favorable for shoot formation. 
		- Option C: High Gibberellin and Low Abscisic Acid can also promote growth but is less specific for shoot formation.
		- Option D: High 2,4-D (an auxin) and High Kinetin (a cytokinin) can lead to ambiguous results, but the high level of 2,4-D makes it more likely to promote callus formation rather than distinct shoot formation.
	3. Determine which option is least likely to promote shoot formation.
		Result: Given that Option D has a high concentration of a growth regulator (2,4-D) that supports callus formation, it is the least favorable for shoot induction.
		Verification: The presence of high Auxin in Option D can lead to inhibited shoot formation and is thus the least likely to promote shoots.
## OPTION ANALYSIS
[A] :x: High Auxin and Low Cytokinin could inhibit shoot formation but does not have the highest inhibition.
[B] :x: Low Auxin and High Cytokinin is favorable for shoot formation.
[C] :x: High Gibberellin and Low Abscisic Acid can support growth but does not directly inhibit shoot formation.
[D] ✓: High 2,4-D and High Kinetin is least likely to promote shoot formation due to the dominance of Auxin effects leading to callus formation.
## LEARNING AIDS
	**Common Mistakes**:
		1. Confusing the roles of Auxins and Cytokinins: Always remember that high Cytokinin promotes shoot formation, while high Auxin can lead to root formation or callus development.
		2. Misinterpreting combinations: Analyze the ratios and concentrations of PGRs carefully to assess their combined effects.
	**Quick Tips**:
		1. Remember the Auxin/Cytokinin ratio for shoot versus root differentiation.
		2. Mnemonic for PGRs: "A Happy Child Grows Abundantly" (Auxin, High Cytokinin for growing shoots, Gibberellin for overall growth, Abscisic Acid for stress responses).

K SUNKANNA · Answer

High Auxin and Low Cytokinin

K SUNKANNA · Answer

Low Auxin and High Cytokinin

K SUNKANNA · Answer

High Gibberellin and Low Abscisic Acid

K SUNKANNA · Answer

The correct Option is "High 2,4-D and High Kinetin"

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