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Question #45970
The Question
In a terrestrial ecosystem, a severe environmental stress inhibits the rate of detritus decomposition, leading to acute nitrogen deficiency in the soil. Based on the principles of plant growth and mineral nutrition, which of the following best explains the subsequent morphogenetic shift observed in the affected plants?
Options
- A.
A drop in endogenous cytokinin synthesis due to nitrogen limitation decreases the cytokinin-to-auxin ratio, suppressing adventitious bud initiation and promoting root elongation.
- B.
Nitrogen deficiency directly inhibits auxin biosynthesis at the shoot apex, increasing the cytokinin-to-auxin ratio and inducing rapid adventitious bud formation.
- C.
The stress induces massive ethylene production, which acts synergistically with cytokinins to shift the metabolic sink from root growth to reproductive development.
- D.
Reduced nitrogen availability blocks the basipetal transport of auxin, causing an accumulation of cytokinins in the shoot that triggers early senescence.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Cytokinin|Auxin|Decomposition|Nitrogen_Availability
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the basic functions of hormones ('Auxin for roots, Cytokinin for shoots') but fail to synthesize across chapters.
This question requires linking Ecology (Decomposition rates affecting nutrient cycling), Mineral Nutrition (Nitrogen as a structural component of purines), and Plant Growth and Development (The biochemical nature of Cytokinins and the morphogenetic impact of the Cytokinin/Auxin ratio during environmental stress).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Plant Growth and Development - Class 11 |
| Concept | Cytokinin-Auxin Ratio |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |