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Question #45982
The Question
A researcher conducts an experiment on a Short-Day Plant (SDP) and a seasonally breeding female mammal. In the plant, the phloem tissue at the base of the leaf is completely girdled (blocked) prior to exposing it to an inductive critical dark period. In the mammal, the hypothalamo-hypophyseal portal blood vessels are surgically severed, while the direct neural tracts to the pituitary are left intact. Which of the following accurately describes the physiological outcome regarding their reproductive transitions?
Options
- A.
A. The plant will flower because phytochrome is synthesized directly in the shoot apex, while the mammal will fail to breed due to the loss of oxytocin release from the pars nervosa.
- B.
B. Both organisms will fail to initiate reproductive phases because the systemic translocation of florigen is blocked in the plant, and GnRH cannot reach the pars distalis in the mammal.
- C.
C. The plant will fail to flower due to the inability of leaves to perceive the photoperiod, while the mammal will continue seasonal breeding as melatonin directly stimulates the gonads.
- D.
D. Both organisms will successfully initiate reproduction because the critical dark period was maintained for the plant, and the pars nervosa will compensate by releasing gonadotropins in the mammal.
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
Photoperiodism Thresholds|Hypothalamo-Hypophyseal Portal System|Pineal Gland
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between the site of stimulus perception and the anatomical pathway required for the systemic effector signal.
Students often confuse the direct neural regulation of the posterior pituitary (pars nervosa) with the portal circulatory regulation of the anterior pituitary (pars distalis), and similarly confuse photoperiod perception in leaves with the necessary phloem-mediated translocation of florigen.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Plant Growth and Development - Class 11 |
| Concept | Photoperiodism Thresholds |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |