Factors affecting transpiration

Factors affecting transpiration

Factors Transpiration Humidity Decreases Increases

Temperature Increases Increases

Wind Increases Increases

Light Increases Increases

Higher conc. of water vapour (100% saturated)

The drier the air, the steeper the concentration gradient, the faster the rate of transpiration.

In plastics bag – 90% humidity

No plastics bag – 70% humidity

Factors affecting transpiration

Factors Transpiration Humidity Decreases Increases

Temperature Increases Increases

Wind Increases Increases

Light Increases Increases

Guard cells turgid

Stoma Opens

Guard cells flaccid

Stoma Closes

day time night time

Stoma

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.

Wilting

What happens to the leaves when they wilt?

Rate of transpiration > rate of absorption of water

• How does wilting benefits the plants?– When leaves fold up, the surface area exposed to

the sunlight is reduced. – Stomata closes – Transpiration decreases

Wilting

• Disadvantages of wilting – Stomata closes– Carbon dioxide cannot diffuse into the leaves– Carbon dioxide becomes the limiting factor for

photosynthesis

Wilting

How to reduce transpiration?

Guard cells

Lower epidermis

Guard cells

Lower epidermis

Desert plant Normal condition

Habitat of marram grass

Leaves of marram grass

Guard cells

Hawaii Silversword

Leaves

Flowers

Guard cells

Lower epidermis

Guard cells

Leaves covered with silver hairs

Guard cells

Lower epidermis

Desert plant Adaptations:

•Sunken stomata

How it helps:

•The enclosed region around the stomata helps to retain water vapour

•increases humidity

Guard cells

Adaptations Functions Leaves curved up Reduce exposure to wind

and high temperature Hairs surround grooves Traps water vapour

Adaptations:

- Leaves covered with silvery white hair

How it helps:

-Reflect light lowers temperature of the leaves