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Question #46292
The Question
A researcher uses Agrobacterium tumefaciens to introduce a genetic construct into a dicot plant, aiming to silence the genes responsible for protoxylem and metaxylem differentiation via RNA interference (RNAi). The resulting transgenic plant exhibits a collapsed vascular cylinder, severe wilting, and a complete halt in the translocation of organic solutes, despite possessing anatomically normal phloem. Which of the following statements is INCORRECT regarding the physiological and anatomical consequences in this plant?
Options
- A.
The structural collapse of the vascular cylinder is due to the failure to form thick, lignified secondary walls characteristic of tracheary elements.
- B.
The RNAi mechanism involves the introduced DNA producing both sense and antisense RNA, which form a dsRNA that initiates the silencing of xylem-specific mRNA.
- C.
The translocation of organic solutes halts because the companion cells lack the ATP required to actively pump water into the sieve tubes to generate turgor pressure.
- D.
The failure of mass flow in the phloem is an indirect consequence of xylem absence, as water from the adjacent xylem must enter the hypertonic sieve tubes via osmosis.
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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
Agrobacterium_Tumefaciens|Protoxylem|Metaxylem|Vascular_Bundle
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the active loading of solutes (sucrose) with the movement of the solvent (water).
A fundamental rule of biology is that water never moves via active transport; it strictly follows osmotic gradients.
This question also tests the integrative understanding that phloem function (organic solute transport) is physically and osmotically dependent on an intact, functioning xylem.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Anatomy of Flowering Plants - Class 11 |
| Concept | Protoxylem vs Metaxylem Arrangement |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |