Xylem transports water in plants primarily through a process called transpiration pull.
Understanding Transpiration Pull
Transpiration, the evaporation of water from leaves, creates a negative pressure, or tension, within the xylem vessels. This tension pulls water upwards from the roots, much like a straw pulls liquid. This upward movement of water is continuous and is driven by the continuous transpiration occurring in all the leaves.
The Mechanism:
- Water Uptake by Roots: Plants absorb water from the soil through their roots. This water moves into the xylem vessels.
- Cohesion and Adhesion: Water molecules stick together (cohesion) and to the xylem walls (adhesion). This creates a continuous column of water extending from the roots to the leaves.
- Transpiration: As water evaporates from the leaves through stomata, it creates a pulling force that draws more water upwards from the xylem.
- Capillary Action: Although less significant than transpiration pull in tall plants, capillary action also plays a minor role in water transport, aided by the narrow diameter of xylem vessels.
Example:
Imagine a drinking straw. Sucking on the straw creates a negative pressure that pulls liquid upwards. Similarly, transpiration in leaves creates a negative pressure (transpiration pull) that draws water up the xylem. This continuous process keeps water moving throughout the plant.
Reference Information:
Continuous transpiration occurring in all of the leaves of a plant creates a negative pressure in the water column (xylem). This exerts an upward pull on the water column, called transpiration pull. And thus, the water present in the xylem column transports up to the tip of the stem, leaves, etc.03-Jul-2022
