1. Factors affecting transpiration

2. Factors affecting transpiration
Humidity
Decreases
Increases
Temperature
Wind
Light
You are saying that temperature would increase the rate of transpiration right.
Temperature is a factor affecting the rate of transpiration.

3. Higher conc. of water vapour (100% saturated)
In plastics bag –
90% humidity
No plastics bag –
70% humidity
Usually the intercellular spaces are full of water vapour -> the spaces are saturated with water vapour.
On the other hand, the concentration of water vapour in the atmosphere, may be 50%, 70%.
Hence there would be a difference in the concentration gradient of the water vapour.
The drier the air outside the leaves, the steeper is this concentration grad, increases the rate of transpiration.
The drier the air, the steeper the concentration gradient, the faster the rate of transpiration.

4. Factors affecting transpiration
Humidity
Decreases
Increases
Temperature
Wind
Light
You are saying that temperature would increase the rate of transpiration right.
Temperature is a factor affecting the rate of transpiration.
Kinetic model of matter
As the tempearture increases, the movement of the molecules increases as well.
Water molecules are able to escape out of the air spaces at a higher rate.
Wind – a layer of water vapour ard the leaves. We cant see this layer
Its take a longer time from water vapout to diffuse arcoss this layer of water vapour.
Removing of water vapour, the humidity surrounding the leaves becomes lower.

5. night time
day time
Guard cells turgid
Stoma Opens
Guard cells flaccid
Stoma Closes
Stoma

6. Think about it!!
Why placing the vegetables in a plastic bag helps to reduce transpiration?
It helps to keep the humidity of the air surrounding the vegetables high.

7. Wilting Rate of transpiration > rate of absorption of water
What happens to the leaves when they wilt?
Wilted leaves are folded and drooping because cells have become flaccid due to the excessive lost of water.
Plants wilt due to the excessive lost of water, cells become flaccid and leaves folds up.
In this case, there is no absorption of water.
There is only transpiration.

8. Wilting How does wilting benefits the plants?
When leaves fold up, the surface area exposed to the sunlight is reduced.
Stomata closes
Transpiration decreases

9. Wilting Disadvantages of wilting Stomata closes
Carbon dioxide cannot diffuse into the leaves
Carbon dioxide becomes the limiting factor for photosynthesis
Water is already lacking, so water is a limiting factor
Now, with the closing of stomata, carbon dioxide becomes the limiting factor for photosynthesis.

10. How to reduce transpiration?

11. Normal condition Desert plant Guard cells Guard cells Lower epidermis

12. Habitat of marram grass Leaves of marram grass
Guard cells
Habitat of marram grass
Leaves of marram grass

13. Hawaii Silversword
Flowers
Leaves

14. Guard cells Guard cells Lower epidermis
Leaves covered with silver hairs

15. Desert plant Adaptations: How it helps: Sunken stomata
The enclosed region around the stomata helps to retain water vapour
increases humidity
Guard cells
Lower epidermis

16. Adaptations Functions Leaves curved up
Guard cells
Adaptations
Functions
Leaves curved up
Reduce exposure to wind and high temperature
Hairs surround grooves
Traps water vapour

17. Adaptations: - Leaves covered with silvery white hair
How it helps: -Reflect light lowers temperature of the leaves