Leaf structure
Leaf structure
- A leaf is adapted for photosynthesis.
- Most leaves are broad (catch light) and thin (gases reach all cells).
- Each tissue has a job.
Practice
Leaves are broad and thin because this:
A large surface area catches light; a thin leaf gives short distances for light and gases.
The parts of a leaf
| Part | Job |
|---|---|
| cuticle | waxy, reduces water loss but lets light through |
| upper epidermis | clear (no chloroplasts) — lets light through |
| palisade mesophyll | tall cells packed with chloroplasts → most photosynthesis |
| spongy mesophyll | rounded cells with air spaces for gas movement |
| stomata + guard cells | tiny holes (mostly underneath) that let CO₂ in / O₂ out; guard cells open/close them |
| vascular bundles | xylem brings water; phloem carries sugars away |
Practice
Most photosynthesis happens in the:
Palisade cells are tall and full of chloroplasts, near the top to catch light.
Practice
Stomata (with their guard cells):
Stomata are pores (mostly on the lower surface) for gas exchange; guard cells open and close them.
Practice
In the leaf's vascular bundles:
Xylem delivers water to the leaf; phloem carries away the sugars made.
You've got it
Key idea
- a leaf is broad (catch light) and thin (gases reach all cells)
- palisade mesophyll does most photosynthesis (packed with chloroplasts)
- stomata (with guard cells) let CO₂ in and O₂ out; air spaces help gas movement
- xylem brings water in; phloem carries sugars away