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 transports substances only upwards, from roots to leaves.
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False. Phloem moves sugars both up and down the plant, from sources to wherever they are needed. Xylem carries water only upwards.
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
Write from dead xylem
- One tissue is made of dead lignified tubes.
- Another tissue carries dissolved sugars up or down.
Which tissue is xylem, and how is phloem different?
Dead lignified tubes are the xylem clue.
Which tissue carries water up the plant?
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Xylem is the one-way water route.