Plant hormones Flashcards
what are auxins and what do they do
a plant growth hormone which controls growth near the tips of SHOOTS AND ROOTS
what is a positive tropism
when a plant grows towards the stimulus ( change in environment)
what is a negative tropism
the plant grows away from the stimulus
what is phototropism
a response to the stimulus of light
what is geotropism
a response to the stimulus of gravity
how do shoots use auxin to grow towards the light
- auxin is produced at the very top of the shoot
- in shoots, auxin triggers cell growth
- light causes auxin to concentrate on the darker side of the shoot tip
- auxin now spreads down the shoot, so cells on the darker side grow faster than cells on the lighter side
- this causes the shoot to grow towards the lught
what direction to plant roots grow
towards the force of gravity
what is photo and geotropism caused by
- unequal distribution of auxin
what happens when shoots grow towards light
- when a shoot tip is exposed to light, more auxin increases on the side that is in the shade than the side thats in the light
- this makes the cells grow and elongate faster on the side in the shade, so the shoot bends towards the light
describe geotropism
- auxin is produced in the root
- but gravity causes the auxin to concentrate on the lower side
- in roots, auxin inhibits cell growth
- so the lower side now grows more slowly than the upper side
- this causes the roots to grow towards the force of gravity
what do gibberellins do
they stimulate plant stems to grow, they are important for seed germination
what is seed germination
the process where seeds sprout and begin to grow
what can gibberellins be used for
ending / controlling seed dormancy
promote flowering
increase fruit size
what is seed dormancy
when seeds will not germinate because of certain conditions, e.g - coldness or dryness
what is ethene and what is it used for in plants
a gas produced by aging parts of a plant, used to stimulate the ripening of a fruit
what are auxins used for in agriculture
- killing weeds
- as rooting powders
- for growing cells in tissue culture
what would happen if the tip of a shoot is removed
no auxin available so shoot may stop growing
what does extra auxin do
promotes growth in the shoot but inhibits growth in the toot
what experiment was used to investigate phototropism
- shine light on shoots
- the shoots will grow in the direction of the light
- cut off the shoots tips
- shoots did not grow towards the light
- scientists suggested the shoot produced a hormone (auxins)
- scientists covered tips of shoots with foil and they didnt grow towards the light, suggesting that the tips are sensitive the light
- they covered the lower parts of the shoots with foil, and the shoots grew towards the light, showing that the lower parts of shoots were not sensitive to the light
why is ethane used
Fruits, such as bananas, are usually harvested before they are ripe. These are then transported long distances and can be stored before they’re needed. Ethene is then used to trigger bananas to ripen just before they’re sold in the uk
