Practise plant coordination questions by tracing Venus flytrap touch responses, auxin acid growth and gibberellin signalling during seed germination.
The Venus fly trap, Dionaea muscipula, is a carnivorous plant. It has traps which catch insects.
Each trap consists of a pair of modified leaves joined by a midrib of hinge cells. The modified leaves have touch-sensitive hairs. If two hairs are touched within 20 seconds, or the same hair is touched twice in rapid succession, the trap closes.
Explain how touching the hairs results in closure of the trap.
any five from:
1. (touching hairs causes), action potential / depolarisation ;
2. auxin increase triggered in hinge cells ;
3. H+/ hydrogen ions, pumped into cell walls ;
4. calcium pectate 'glue' in cell wall dissolved ;
5. Ca2+ ions enter hinge cell ;
6. water follows by osmosis ;
7. hinge / midrib, cells expand ;
8. trap lobes, flip from convex to concave / change in elastic tension ;
There are more than 600 plant species in the genus Ipomoea. Many species are grown for their attractive flowers, and some species are used as crop plants.
Scientists are researching whether abscisic acid can be used in crop treatment to increase yield. Evidence suggests that abscisic acid modifies the effect of auxin on elongation growth in plants.
The passage outlines the role of auxin in elongation growth in plants.
Complete the passage by using the most appropriate scientific terms.
The binding of auxin to receptors causes ...... to be pumped into cell walls.
This activates proteins called expansins, which disrupt the links between ...... microfibrils. The cell walls are then able to expand.
1 protons / H+(ions) ;
2 cellulose ;
When a dormant seed absorbs water it will start to germinate and its rate of respiration will increase.
Name the plant growth regulator involved in the initiation of germination of seeds.
gibberellin ;