Which of these is an example of gravitropism?

Options

A. vines growing around an object they touch
B. roots growing into the ground
C. plants growing towards light
D. responses of plants to seasonal changes in length of nights

Answer

**Step-by-Step Solution:**

1. **Understanding Gravitropism**: Gravitropism, also known as geotropism, is the growth of plant organs in response to gravity. Roots typically exhibit positive gravitropism, growing downward towards the gravitational pull, while stems show negative gravitropism, growing upward away from gravity.

2. **Analyzing the Options**: The question provides several options to identify which one exemplifies gravitropism. We need to evaluate each option based on the definition of gravitropism.

3. **Option 1 - Vines Growing Around an Object**: This option describes vines that wrap around objects they come into contact with. This behavior is known as thigmotropism, not gravitropism. Therefore, this option is incorrect.

4. **Option 2 - Root Growing into the Ground**: This option describes roots growing downward into the soil. Since roots grow in the direction of gravity, this is a clear example of positive gravitropism. Hence, this option is correct.

5. **Option 3 - Plants Growing Towards Light**: This option refers to phototropism, where plants grow towards light sources. This is not related to gravitropism, making this option incorrect.

6. **Option 4 - Responses of Plants to Seasonal Changes**: This option refers to photoperiodism, which is the response of plants to the length of day and night. This is unrelated to gravitropism, so this option is also incorrect.

7. **Conclusion**: After evaluating all the options, the correct answer is option 2, "Root growing into the ground," as it exemplifies gravitropism.

**Final Answer**: The correct example of gravitropism is **Root growing into the ground** (Option 2).

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