Leaves
Science: KS3, topic 1.1.12
Leaves
Leaves are examples of plant organs made up of different types of tissue:
Epidermal tissue
- Epidermal tissue covers the outer surface of leaves (as well as the rest of the plant).
Palisade mesophyll
- Palisade mesophyll is a row of cells located below the upper epidermis.
- The cells are exposed to a lot of sunlight.
- The cells have lots of chloroplasts (where photosynthesis takes place) to maximise the energy transfer in photosynthesis.
Spongy mesophyll
- Spongy mesophyll contains many air spaces, which help with gas exchange throughout the leaf.
Stomata
- Found in the lower epidermis, these gaps facilitate (make easier) the diffusion of gases in and out of the leaf, if they are open.
- When necessary, specialised (perform a specific function) guard cells are capable of closing these gaps.
- e.g. in hot weather to reduce water loss.
Test yourself on Leaves
Select the correct statement about leaf tissues
What do guard cells do to help a leaf in hot weather?
What would happen to gas exchange if a leaf's stomata stayed closed all the time?