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Question #46278

Difficulty: 8/10 | 🟢 Free

The Question

A transgenic plant of the family Solanaceae is engineered to exhibit Kranz anatomy for enhanced carbon fixation. However, a targeted mutation completely inhibits the conversion of the phytochrome $P_r$ form to the $P_{fr}$ form. Despite exposure to an optimal inductive photoperiod and possessing a high metabolic energy surplus, the plant fails to flower. Which of the following statements correctly identifies the physiological reason for this failure?

Options

A.
The mutation prevents the synthesis of florigen directly in the shoot apical meristem, leaving the characteristic $\oplus \text{O}_+ \text{K}_{(5)} \text{C}_{(5)} \text{A}_5 \underline{\text{G}}_{(2)}$ floral blueprint unexpressed.
B.
The absence of the physiologically active $P_{fr}$ form prevents florigen synthesis in the leaves and its subsequent translocation via the phloem to the shoot apices.
C.
The high metabolic cost of maintaining the engineered $C_4$ pathway depletes the ATP required for the enzymatic conversion of $P_r$ to $P_{fr}$ in the bundle sheath cells.
D.
The inability to form $P_{fr}$ triggers developmental plasticity, causing the plant to permanently revert to a $C_3$ cycle to conserve energy for vegetative growth.

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Comparative_Analysis

Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.

Concepts Behind This Question

Solanaceae Floral Formula|Phytochrome Interconversion|Kranz Anatomy Adaptations

Why This Question Is Tricky

Common Mistakes

Location Trap & Signaling vs.

Metabolism.

The conceptual pivot tests two common misconceptions: first, confusing the site of florigen synthesis (leaves) with its site of action (shoot apex); second, assuming that a massive metabolic surplus (via C4 engineering) can bypass or override the primary photoperiodic signaling axis (Phytochrome -> Florigen) required for morphogenetic shifts.

Quick Facts About This Question

Question Information

Subject	Biology
Chapter	Morphology of Flowering Plants - Class 11
Concept	Solanaceae Floral Formula
Difficulty	8
Cognitive Load	5
Target Solve Time	120 sec
Access	Free