Control and coordination in plants
Control and coordination in plants
- Plants coordinate too — even fast enough to catch an insect.
- They use electrical signals and plant hormones.
- Two key hormones: auxin and gibberellin.
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.
Practice
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.
Practice
Plants can use electrical signals as well as hormones to coordinate responses.
The Venus fly trap shows plants use fast electrical signals; hormones like auxin and gibberellin act more slowly.
Auxin and growth
- Auxin makes cells grow longer (elongation).
- It makes the cell pump protons into the cell wall, which acidifies and loosens the wall.
- The cell can then stretch as water enters.
Practice
Auxin causes cell elongation by:
Auxin acidifies the wall (via proton pumping), loosening it so the cell stretches as water enters.
Gibberellin and germination
- Gibberellin controls the germination of barley seeds.
- It switches on the genes that make amylase.
- Amylase breaks down stored starch into sugars to feed the growing seedling.
Practice
Gibberellin helps a barley seed germinate by:
Gibberellin activates amylase production; amylase digests stored starch into sugars to feed the seedling.
You've got it
Key idea
- 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)