Leaf structure
Introduced| English | Meaning |
|---|---|
| adaptation/ˌædæpˈteɪʃn/ | A characteristic that helps an organism survive and reproduce in its environment. |
| palisade/ˈpælɪseɪd/ | palisade |
| chloroplasts/ˈklɔːrəʊplæsts/ | Organelles in plants and algae that contain photosynthetic pigments and carry out photosynthesis. |
| veins/veɪnz/ | A blood vessel that carries blood towards the heart. |
| xylem/ˈzaɪləm/ | Plant vascular tissue that transports water and mineral ions and helps support the plant. |
| phloem/ˈfləʊɪm/ | Plant vascular tissue that transports sugars and other organic substances between sources and sinks. |
| stomata/ˈstəʊmətə/ | Small pores in plant epidermis, controlled by guard cells, through which gases and water vapour pass. |
| guard cells/ɡɑːd selz/ | One of a pair of specialised cells whose changes in shape control the opening of a stoma. |
The perfect solar panel
- A leaf looks simple, but it's beautifully built to capture light and make food.
- Almost every feature is an adaptation 适应 for photosynthesis.
A leaf is broad and flat mainly to:
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Large surface area maximises light capture.
A leaf is ______ so that gases can diffuse in and out over short distances.
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Thinness shortens the diffusion distance.
Built for light
- A leaf is broad and flat for a large surface area to catch light.
- It is thin, so gases diffuse in and out quickly.
A leaf in cross-section: each tissue is adapted for photosynthesis and gas exchange
Inside a leaf
Tap each layer of a leaf cross-section to see how its structure is built for photosynthesis and gas exchange.
Which leaf layer contains the most chloroplasts?
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The palisade layer near the top absorbs the most light.
Inside the leaf
- The upper palisade 栅栏组织 layer is packed with chloroplasts 叶绿体 to absorb the most light.
- A network of veins 静脉 (xylem 木质部 and phloem 韧皮部) brings water and carries away sugars.
Stomata 气孔 in the lower surface of a leaf
Stomata are pores that allow:
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Stomata let CO₂ in and O₂ out.
Guard cells open and close the stomata.
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They control gas exchange and water loss.
Gas exchange
- Tiny pores called stomata (on the underside) let carbon dioxide in and oxygen out.
- Guard cells 保卫细胞 open and close the stomata to control gas exchange and water loss.
Worked example. A leaf's broad, thin shape gives a large surface area and short diffusion distance — letting it absorb plenty of light and exchange gases quickly. Form fits function.
What a plant does with the glucose it makes
You've got it
- a leaf is broad and flat (large surface area) and thin (fast diffusion)
- the palisade layer holds the most chloroplasts; veins carry water and sugar
- stomata (controlled by guard cells) let CO₂ in and O₂ out