1. TRANSPIRATION

2. Learning Objectives
• Explain the mechanism of water uptake and movement in terms of transpiration producing a tension (‘pull’) from above, creating a water potential gradient in the xylem, drawing cohesive water molecules up the plant.
Define transpiration as evaporation of water at the surfaces of the mesophyll cells followed by loss of water vapour from plant leaves, through the stomata
• Describe how water vapour loss is related to cell surfaces, air spaces and stomata
• Describe the effects of variation of temperature, humidity and light intensity on transpiration rate
• Discuss the adaptations of the leaf, stem and root to three contrasting environments, to include pond, garden and desert, with emphasis on local examples (where appropriate) and the factors described in the core

3. Need for transport systems
Plants need sugars and water to stay alive
Water needs to travel from the roots to the leaves
Sugars need to travel from the leaves to the rest of the plant
Importance of water

4. Water Movement Through a Plant

5. Transport System in Plants
Functions?
Vascular bundle
Xylem
Phloem
Sieve tubes
Companion cell
Label the terms

6. How is transpiration regulated?
Transpiration is the release of water vapour from a plant through the leaves, causing water to move through the plant.
Regulation is done by guard cell
Number of stomata
Video:

7. Tiny pores found on the surfaces of a leaf
Tiny pores found on the surfaces of a leaf
Stomata take in carbon dioxide from the air through stomata
Water vapour passes out from the leaf to the atmosphere through stomata

8. Which factors affect the transpiration?
Atmospheric conditions
Leaf Structure

9. Atmospheric Structure
Leaf Structure
Atmospheric Structure
Wind
High temperature
Low hımidity
High light intensity
Thick and waxy cuticle
Stomata sunk
Humid air
Leaves shape (needle)
Transpiration Rate