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Question #46824
The Question
In mature dicot stems, the transition of older secondary xylem into heartwood (duramen) represents a terminal developmental phase where cells permanently exit the cell cycle (G0-equivalent) and undergo specific structural and chemical changes. Suppose a genetic defect prevents this terminal transition, specifically inhibiting the deposition of organic compounds in the central wood. Which of the following statements regarding this mutated tree is INCORRECT?
Options
- A.
The central innermost layers of the stem will lack tannins and resins, making the tree highly susceptible to the attacks of microorganisms and insects.
- B.
The primary and older secondary phloem will avoid being crushed, as the central wood fails to harden into a rigid heartwood core.
- C.
The peripheral region of the secondary xylem (alburnum) will remain lighter in color and continue its normal function of water conduction.
- D.
The tree will experience a reduction in mechanical support, as the central wood fails to develop the characteristic extractive-filled dead elements.
Check Your Answer
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
Heartwood|G0 Phase Quiescence|Terminalization of Chiasmata
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often conflate the physical 'hardness' of heartwood with the outward mechanical pressure that crushes the peripheral phloem.
The trap tests the exact NCERT mechanism of phloem crushing, which is driven by continuous cambial activity and the accumulation of secondary xylem, independent of the chemical transition into heartwood.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Anatomy of Flowering Plants - Class 11 |
| Concept | Heartwood vs Sapwood |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |