Which factor determines the direction of movement of main root and stem?

Options

A. Oxygen
B. Gravity
C. Temperature
D. Nutrients

Answer

To determine the factor that influences the direction of movement of the main root and stem in plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Plant Movement**:
- Plants exhibit different types of movements, particularly in their roots and stems. These movements are responses to environmental stimuli.

2. **Identifying the Types of Geotropism**:
- Roots typically grow downwards, which is known as positive geotropism. This means they grow in the direction of gravitational pull.
- Stems, on the other hand, generally grow upwards, which is referred to as negative geotropism. This indicates that they grow against the direction of gravity.

3. **Role of Gravity**:
- Gravity is a significant factor that influences the growth direction of both roots and stems. The roots grow towards gravity (downwards), while the stems grow away from gravity (upwards).

4. **Excluding Other Factors**:
- Other environmental factors such as oxygen, temperature, and nutrient availability do not primarily determine the direction of growth for roots and stems. They may affect growth rates or overall health, but not the directional movement.

5. **Conclusion**:
- Therefore, the primary factor that determines the direction of movement of the main root and stem is gravity.

### Final Answer:
The direction of movement of the main root and stem is determined by gravity.

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