Water Transport
Mediumbiology
The cohesion-tension theory explains ascent of sap primarily due to:
Select the correct option:
Solution
Incorrect! Answer:
Transpirational pull with cohesion
- The Challenge: Plants must move water from roots to leaves, often against gravity over great heights.
- Cohesion-Tension Theory: Proposed by Dixon and Joly.
- 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.
- 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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About This Question
- Subject
- biology
- Chapter
- plant physiology
- Topic
- water transport
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
Transpirational pull with cohesion
- The Challenge: Plants must move water from roots to leaves, often against gravity over great heights.
- Cohesion-Tension Theory: Proposed by Dixon and Joly.
- 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.
- Mechanism: This tension pulls the continuous water column upward like a rope. This is the primary driver for the ascent of sap.
This medium difficulty biology question is from the chapter plant physiology, covering the topic of water transport. It appeared in the 2025 exam.
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