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Multiple Choice
When do short-day plants and long-day plants typically flower?
A
Short-day plants flower when days are longer than a critical length; long-day plants flower when days are shorter than a critical length.
B
Short-day plants flower when nights are longer than a critical length; long-day plants flower when nights are shorter than a critical length.
C
Both short-day and long-day plants flower only during continuous darkness.
D
Short-day plants and long-day plants flower regardless of day or night length.
Verified step by step guidance
1
Understand the concept of photoperiodism: Photoperiodism is the physiological reaction of organisms to the length of day or night. In plants, it influences flowering and other developmental processes.
Learn the distinction between short-day plants and long-day plants: Short-day plants require nights longer than a critical length to flower, while long-day plants require nights shorter than a critical length to flower.
Clarify the role of darkness: It is the duration of uninterrupted darkness (night length) that determines flowering in these plants, not the length of daylight. This is why the terms 'short-day' and 'long-day' are somewhat misleading.
Analyze the incorrect statements: The statement 'Short-day plants flower when days are longer than a critical length' is incorrect because short-day plants flower when nights are longer than a critical length. Similarly, 'Both short-day and long-day plants flower only during continuous darkness' is incorrect because flowering depends on the specific duration of darkness, not continuous darkness.
Conclude with the correct explanation: Short-day plants flower when nights are longer than a critical length, and long-day plants flower when nights are shorter than a critical length. This aligns with the correct answer provided in the problem.