Water Transport

Question

The cohesion-tension theory explains ascent of sap primarily due to:

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1. **The Challenge**: Plants must move water from roots to leaves, often against gravity over great heights.
2. **Cohesion-Tension Theory**: Proposed by Dixon and Joly.
3. **Key Components**:
   - **Cohesion**: The strong mutual attraction between water molecules due to hydrogen bonding.
   - **Adhesion**: Attraction of water molecules to the walls of xylem vessels.
   - **Transpirational Pull**: As water evaporates from leaf stomata ($transpiration$), it creates a negative pressure or 'tension' in the xylem.
4. **Mechanism**: This tension pulls the continuous water column upward like a rope. This is the **primary** driver for the ascent of sap.

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Water Transport

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