Problem 7 - AP Psychology Premium Prep 2021

Question

Mimosa pudica is a plant often called the "sensitive plant" because when you touch the leaves, they immediately close up. One theory about the purpose of this type of movement is that herbivores avoid the plant due to this movement. The movement of Mimosa pudica is an example of (A) phototropism (B) gravitropism (C) aquatropism (D) thigmotropism

Step-by-Step Solution

Answer

The movement of Mimosa pudica, as it closes its leaves upon touch, is an example of (D) Thigmotropism.

Step 1: Identifying phototropism

Phototropism is the growth or movement of a plant in response to light. Since the movement of Mimosa pudica is triggered by touch and not light, this option is not correct.

Step 2: Identifying gravitropism

Gravitropism is the growth or movement of a plant in response to gravity. The stem typically grows upward, and the roots grow downward. However, the movement in Mimosa pudica is not in response to gravity but to touch. So this option is not correct.

Step 3: Identifying aquatropism

Aquatropism refers to the growth or movement of a plant in response to water. This type of movement occurs when roots grow towards a water source. Since the movement in Mimosa pudica is not in response to water, but to touch, this option is not correct.

Step 4: Identifying thigmotropism

Thigmotropism is the growth or movement of a plant in response to touch or contact with a surface. This type of response is demonstrated by the Mimosa pudica plant when its leaves close up upon being touched. Therefore, this is the correct option.

Step 5: Conclusion

The movement of Mimosa pudica, as it closes its leaves upon touch, is an example of (D) Thigmotropism.