PPEs revision Flashcards
What is the function of the auxin?
Control growth at the tips of the shoots and the roots.
What do the auxins do?
They dissolve in the solutions of the cell. They then diffuse backwards along the shoots and the roots.
What does auxins do at the roots?
Inhibit growth
What does auxins do at the shoots?
Stimulate growth
What is it called when a plant responds to light?
Phototropism
What is it called when a plant responds to gravity?
Geotropism
What side will the auxins accumulate?
They will either go on the shaded side or the lower side.
What are the shoots positively and negatively?
They positively phototropic and negatively gravitropic
What does it mean to be positively phototropic?
Grow towards the light
What does it mean to be positively gravitropic?
Grow towards the gravity
What are the roots positively and negatively?
They are negatively phototropic and negatively gravitropic
What causes plants to grow towards the light?
Auxins accumulate on the shaded side. Therefore the cells on the shaded sides grow faster which causes the plant to bend to the light.
What causes the roots to curve downwards?
If exposed to light the auxins will accumulate on the lower shaded side and in the roots auxins inhibit growth which t hem causes the upper side to grow faster
What are the 3 uses of auxins?
- To grow plant clones
- To grow plant cuttings
- To kill weeds
How does auxins kill plants?
By adding a lot of auxins it can disrupt the plants growth patterns
What are 3 uses of gibberellin?
- Controlling dormancy
- Inducing Flowering
- Grow larger fruits
How does gibberellin control dormancy?
Induces germination at certain times of the year when plants dont have the right conditions to grow
How does gibberellin induce flowering?
Flowers need certain conditions to grow but gibberellin allows flowers to grow on demand which can allow farmers to grow bigger and more flowers
How does gibberellin help growing larger fruits?
It is useful for seedless fruits that naturally dont grow as seeded fruits. Gibberellin allows the fruits to grow well.
What is the used of the hormone ethene for plants?
Stimulate the ripening of fruits by stimulating a hormone.
What 3 factors affect diffusion?
Distance, concentration difference and surface area
rate of diffusion is proportional to…
surface area x concentration difference / thickness of membrane
What happens if the surface area or the difference in concentration doubles?
The rate of diffusion will double
What happens if the thickness of membrane halves?
The rate of diffusion will half
What is thermoregulation used for?
To control our internal body temperature
Which part of the brain controls thermoregulation?
Hypothalamus
What mechanisms does the body use to warm us up?
- The blood vessels that lie on the surface of the skin constrict to decrease the amount of blood that flows near the surface. This then decreases the amount of heat energy lost
- Contraction of erector muscles to trap a small layer of insulating air
- We shiver which is caused by the muscles contracting automatically
What mechanisms does the body use to cool us down?
- Erector muscles relax causing the hairs to fall flat
- The blood vessels expand to allow more heat energy to transfer to the surroundings as it is closer to the skin surface
- We produce sweat which is a mixture of water and salt so when it evaporates it takes heat energy away from the skin
