Plants Flashcards
Define tropism
Growth movement in response to stimulus
Describe negative tropism
Growing away from stimulus
Describe positive tropism
Towards stimulus
Describe negative phototropism
Growth away from light
Describe geotropism
Growth away from light
Auxin function
Promotes growth
Causes of tropisms
- sunlight breaks down auxin
- area of plant with shade= auxin accumulates
- more growth on shaded side
= lop sided growth
Why do plants compete
- light and water
- nutrients
- space
Define phototropism
Shoots growing towards the light
Where is auxin produced
The tips of the plant
Describe how auxin works
- light causes auxin to concentrate on the darker side of the shoot tip
- auxin now spreads down the shoot
- cells on darker side grow faster than cells in lighter side
= causes shoot to grow towards light
Define geotropism
Plants growing towards gravity
(Downwards)
Describe how geotropism works
- auxin produced at the root
But - gravity causes auxin to concentrate on lower side
= lower side grows more slowly than upper side
Use of giberellins
Starting the germination of seeds
Use of ethene
Controls cell division and the ripening of fruits
Uses of auxins in farming etc
- weed killers
- rooting powders
- promoting growth in tissue culture
Uses of giberellins in farming etc
- end seed dormancy
- encourage plants to flower
- grow larger fruit
Use of ethene eg farming
- tigger bananas to ripen just before they are sold in the UK
Function of fertilisers
Increase growth and reproduction of algae
= more food for plants
= higher plant population
Use of auxin in roots
Inhibits cell growth
= lower side grows slower than upper side
= cause roots to grow towards force of gravity
