Control and coordination in plants
| English | Chinese | Pinyin |
|---|---|---|
| auxin | 生长素 | shēng zhǎng sù |
| gibberellin | 赤霉素 | chì méi sù |
| elongation | 伸长 | shēn cháng |
| germination | 萌发 | méng fā |
| amylase | 淀粉酶 | diàn fěn méi |
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 ______.
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.
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:
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:
Auxin acidifies the wall (via proton pumping), loosening it so the cell stretches as water enters.
Put positive phototropism in order.
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:
Gibberellin activates amylase production; amylase digests stored starch into sugars to feed the seedling.
Match each plant signal to what it does.
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)