Xylem and phloem
Introduced| English | Meaning |
|---|---|
| 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. |
| lignin/ˈlɪɡnɪn/ | A strong organic material deposited in some plant cell walls to provide support and waterproofing. |
| translocation/trænsləʊˈkeɪʃn/ | translocation |
A plant's plumbing
- A tall tree must move water up from its roots and sugars down from its leaves — without a heart.
- It uses two transport tissues: xylem 木质部 and phloem 韧皮部.
Xylem and phloem route
Watch water and sugar move through different plant transport tissues.
Xylem transports:
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Xylem carries water and minerals upward.
Xylem vessels are strengthened with:
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Lignin strengthens xylem and helps support the plant.
Xylem
- Xylem carries water and minerals from the roots up to the leaves.
- It is made of dead, hollow tubes strengthened with lignin 木质素 — which also support the plant.
Xylem carries water up in dead lignified tubes; phloem carries sucrose in living cells
Phloem transports:
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Phloem carries sugars (translocation).
The transport of sugars in the phloem is called ______.
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Translocation moves food around the plant.
Phloem
- Phloem carries sugars (food) made in the leaves to the rest of the plant.
- It moves substances both up and down — this is translocation 转运.
A stem in cross-section: the red-stained xylem sits in vascular bundles near the edge
Phloem can transport substances both up and down the plant.
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Translocation moves sugars to wherever they are needed.
Xylem vs phloem
- Xylem: dead cells, one way (up), carries water + minerals.
- Phloem: living cells, both ways, carries sugars.
Xylem goes one way; phloem goes both ways. Water only travels up the xylem (root to leaf). Sugars in the phloem travel to wherever they're needed — up to growing shoots or down to the roots.
You've got it
- xylem carries water + minerals up (dead, lignified tubes that also support)
- phloem carries sugars both ways — translocation
- xylem = one-way, dead; phloem = two-way, living