Transpiration - Water Movement through Plants

Overview

Transpiration is the loss of water from a plant in the form of water vapor. Water is absorbed by roots from the soil and transported as a liquid to the leaves via xylem. In the leaves, small pores allow water to escape as a vapor and CO₂ to enter the leaf for photosynthesis. Of all the water absorbed by plants, less than 5% remains in the plant for growth and storage following growth. This lesson will explain why plants lose so much water, the path water takes through plants, how plants might control for too much water loss to avoid stress conditions, and how the environment plays a role in water loss from plants.

Objectives:

At the completion of this lesson, students will be able to:

1. Define transpiration and explain why it occurs in plants.
    
2. Follow the pathway that water takes through plants from root uptake to evaporation at leaf cell surfaces.
    
3. Describe how the driving force for water movement and any resistances to its flow through the plant are the two major components controlling rates of transpiration.
    
4. Describe how environmental conditions alter rates of transpiration.
    
5. Explain how the plant is able to alter rates of transpiration.