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Question #47553
The Question
The vascular cambium in a dicot stem exhibits strict meristematic polarity, cutting off secondary xylem towards the inner side and secondary phloem towards the outer side. If a targeted mutation completely disrupts the Polar Auxin Transport (PAT) by mislocalizing PIN efflux carriers, reversing the established hormonal gradient across the cambial initials, which of the following represents the most likely anatomical consequence?
Options
- A.
Meristematic polarity will invert, causing secondary xylem to differentiate externally and secondary phloem internally, leading to structural collapse of the conducting system.
- B.
The cambial ring will become more active on the outer side, producing a massive amount of secondary phloem that crushes the primary xylem.
- C.
The cambial initials will undergo rapid redifferentiation into interfascicular parenchyma, permanently halting secondary growth.
- D.
The vascular cambium will functionally mimic the phellogen, cutting off suberized phellem towards the periphery and phelloderm towards the pith.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Vascular Evolution Sequence|Gymnosperm Pollination Geometry|Ovule Exposure
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Failing to distinguish between the 'rate of cambial activity' and 'meristematic polarity'.
Students memorize that cambium is more active on the inner side and might assume hormonal disruption only flips this activity rate (Option B).
However, the auxin gradient dictates the actual spatial differentiation (xylem vs. phloem identity), meaning a reversal leads to a catastrophic structural inversion (Option A).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Plant Kingdom - Class 11 |
| Concept | Vascular Evolution Sequence |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |