Control and coordination in plants
Introduced| English | Meaning |
|---|---|
| auxin/ˈɔːksɪn/ | A class of plant hormones involved in growth responses, including cell elongation and tropisms. |
| gibberellin/ˌdʒɪbəˈrelɪn/ | A plant hormone involved in processes such as stem elongation, seed germination and growth. |
| elongation/iːˌlɒnˈɡeɪʃn/ | An increase in length, such as growth that makes plant cells longer. |
| germination/ˌdʒɜːmɪˈneɪʃn/ | The resumption of growth of a seed embryo, developing into a seedling under suitable conditions. |
| amylase/ˈæmɪleɪz/ | An enzyme that breaks starch into smaller sugars. |
How plants sense and respond
- Plants coordinate too — even fast enough to catch an insect.
- They use electrical signals and plant hormones.
- Two key hormones: auxin 生长素 and gibberellin 赤霉素.
A directional plant growth response to a stimulus (such as light) is called a ______.
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e.g. phototropism is growth towards light; gravitropism is growth in response to gravity.
The Venus fly trap
- Its trap-like leaves carry tiny hairs.
- When an insect touches the hairs, a fast electrical signal spreads.
- The cells quickly lose water and change shape, so the trap snaps shut.
Plants can use fast electrical signals as well as slower hormones to coordinate responses.
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The Venus fly trap shows plants use fast electrical signals; hormones like auxin and gibberellin act more slowly.
The Venus fly trap snaps shut because:
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An insect touching the trigger hairs starts a rapid electrical signal; the cells change shape and the trap closes.
Auxin and growth
- Auxin makes cells grow longer (elongation 伸长).
- It makes the cell pump protons into the cell wall, which acidifies and loosens the wall.
- The cell can then stretch as water enters.
Auxin makes the cell pump protons into the wall, loosening it so the cell can elongate
Phototropism: bending to the light
Step through it. Auxin gathers on the shaded side, makes those cells grow longer, and the shoot bends towards the light.
Auxin causes cell elongation by:
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Auxin acidifies the wall (via proton pumping), loosening it so the cell stretches as water enters.
Put positive phototropism in order.
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Auxin gathers on the shaded side and makes it grow faster, so the shoot leans towards the light.
Gibberellin and germination 萌发
- Gibberellin controls the germination of barley seeds.
- It switches on the genes that make amylase 淀粉酶.
- Amylase breaks down stored starch into sugars to feed the growing seedling.
Gibberellin helps a barley seed germinate by:
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Gibberellin activates amylase production; amylase digests stored starch into sugars to feed the seedling.
Match each plant signal to what it does.
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Auxin and gibberellin are slow hormones; the fly trap uses a fast electrical signal — plants use both.
You've got it
- plants coordinate with electrical signals and hormones
- Venus fly trap: touch hairs → fast electrical signal → cells lose water → trap snaps shut
- auxin → cell elongation (pumps protons → acidifies/loosens the wall)
- gibberellin → germination (switches on amylase → starch → sugars)