Pores of the leaf
Stomata, gas exchange and transpiration.
A wet cloth on a hot day
A wet cloth hung in the sun dries fast. Water leaves it as vapour. A leaf also loses water vapour.
Where do you think the vapour leaves a leaf?
What this lesson covers
The idea
Pores in the leaf epidermis called stomata allow gaseous exchange and transpiration, the evaporation of water vapour through stomata; transpiration creates a pull in the xylem that helps transport water, and helps eliminate wastes.
A wet cloth on a hot day
A wet cloth hung in the sun dries fast. Water leaves it as vapour. A leaf also loses water vapour.
Where do you think the vapour leaves a leaf?
- Through tiny pores in the leaf surface
- Through the roots
- Through the cuticle only, which is waxy
Open the stomata
Open the stomata and watch the gases, the water vapour and the water in the xylem.
Stomata and transpiration
In leaves the epidermis has pores called stomata. Besides gaseous exchange, stomata help in transpiration: the evaporation of water vapour through stomata. Transpiration helps water transport by creating a transpiration pull in the xylem. It also helps in the elimination of wastes from the plant body.
Notes
Stomata are pores in the leaf epidermis. They allow gaseous exchange and transpiration, which creates a pull in the xylem and helps remove wastes.
Check yourself
Stomata are…
Transpiration is…
What does transpiration create in the xylem?
- hairs on the root. Those are root hairs.
- pores in the epidermis of leaves — correct. Yes.
- tubes that carry food. Those are sieve tubes in phloem.
- making food using sunlight. That is photosynthesis.
- absorbing water through root hairs. That is absorption.
- evaporation of water vapour through stomata — correct. Yes.
- A transpiration pull that helps water rise — correct. Yes.
- A push that sends food down. Food moves in the phloem, not by this pull.
- A waxy layer. The waxy layer is the cuticle.