Mimosa plants spread their leaflets during the day and fold them at night. You decide to design an experiment to test whether Mimosa's leaf movements are controlled by a biological clock. Which of the following experiments would be the best test of your hypothesis?
A)Growing the plant indoors and turning the lights on in the middle of the night. If a biological clock is controlling leaf movement, the leaves will open.
B)Putting the plant in a dark closet in the middle of the day. If the leaves close, a biological clock mechanism is ruled out.
C)Subjecting the plant to a flash of red light in the middle of the night. If the leaves open at the usual time the next morning, a biological clock mechanism is ruled out.
D)Putting the plant in a dark closet at nightfall. Check on the plant in the morning about 10 hours later, while the plant is still in the closet. If the leaves are open, a biological clock is indicated.

Question

Quizplus · Accepted Answer

Option D is the best choice because it involves isolating the plant in darkness over a period of time that is long enough to indicate the presence of a biological clock. If the leaves are open after 10 hours, it would suggest that the plant has an internal clock set to a 24-hour period. Option A would not be a good test because the sudden change in light might trigger the leaves to open for reasons other than the biological clock. Option B would not be a good test because the darkness might cause the leaves to close due to normal responses to environmental stimuli. Option C would not be a good test because the flash of light might confuse the plant without providing any useful data.

Mimosa Plants Spread Their Leaflets During the Day and Fold