Cohesion-Tension-Transpiration Pull Model
The most accepted theory explaining long-distance water transport in plants, driven by transpiration and the cohesive properties of water.
What is Cohesion-Tension-Transpiration Pull Model?
The attraction between molecules of the same substance (e.g., water molecules attracting each other via hydrogen bonds).
Key points
- Explain the mechanism of water transport in plants.
- Identify the driving force behind the ascent of sap.
- Describe the roles of cohesion and adhesion in water transport.
- Differentiate between transpiration pull and root pressure.
Common exam trap
Confusing transpiration pull with root pressure as the primary driving force for tall trees.
Definitions
- Term
Cohesion
- Meaning
The attraction between molecules of the same substance (e.g., water molecules attracting each other via hydrogen bonds).
- Term
Adhesion
- Meaning
The attraction between molecules of different substances (e.g., water molecules attracting xylem wall molecules).
- Term
Transpiration
- Meaning
The process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers, through stomata.
- Term
Xylem
- Meaning
The vascular tissue in plants that conducts water and dissolved nutrients upward from the root and also helps to support the plant.
- Term
Tension
- Meaning
A state of being stretched or strained; in this context, a negative pressure or pull.
Learning objectives
Explain the mechanism of water transport in plants.
Identify the driving force behind the ascent of sap.
Describe the roles of cohesion and adhesion in water transport.
Differentiate between transpiration pull and root pressure.
Prerequisites
Structure and function of xylem
Concept of transpiration
Properties of water (cohesion, adhesion, surface tension)
Osmosis and diffusion
Common mistakes
Confusing transpiration pull with root pressure as the primary driving force for tall trees.
Underestimating the role of water's cohesive properties.
Assuming active transport is involved in water movement up the xylem.
Ignoring the contribution of adhesion to the water column's stability.
Keywords
Cohesion
Adhesion
Transpiration
Xylem
Water Transport
Ascent of Sap
Tension
Dixon-Joly Theory
Capillary Action
Water Potential
Practice preview
Which of the following statements about the Cohesion-Tension-Transpiration Pull Model is INCORRECT?…
medium
Which of the following is the primary driving force for the ascent of sap in tall trees, according to the Cohesion-Tension-Transpiration Pull Model?…
easy
The cohesive property of water, crucial for the Cohesion-Tension-Transpiration Pull Model, refers to:…
easy