Guttation results from -

Options

A. A high water potential of the leaves than of roots
B. Root pressure causing water to flow up through xylem faster than it can be lost by transpiration.
C. The pressure flow of sap through phloem
D. A water vapour breaks in the column of xylem sap.

Answer

**Step-by-Step Solution:**

1. **Understanding Guttation:**
Guttation is the process where water is expelled from the leaves of a plant in the form of droplets. This typically occurs at night or early morning when transpiration rates are low.

2. **Identifying the Mechanism of Guttation:**
The primary mechanism responsible for guttation is root pressure. Root pressure is the pressure exerted in the roots of plants that helps in the upward movement of water through the xylem.

3. **Analyzing the Options:**
- **Option 1:** A high water potential of leaves, then that of root.
- This is incorrect because guttation is not primarily due to the water potential difference between leaves and roots.
- **Option 2:** Root pressure causing water to flow through xylem faster than it can be lost by transpiration.
- This is correct. Root pressure pushes water up through the xylem, and if transpiration is low, this excess water is expelled as droplets.
- **Option 3:** The pressure flow of sap through phloem.
- This is incorrect as phloem is involved in the transport of nutrients, not in the process of guttation.
- **Option 4:** A water vapor breaks the column in xylem sap.
- This is also incorrect because if the water column in the xylem breaks, it would hinder the movement of water, not facilitate guttation.

4. **Conclusion:**
Based on the analysis, the correct answer is **Option 2**: Root pressure causing water to flow through xylem faster than it can be lost by transpiration.

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