Homeostasis - plant hormones Flashcards
what is phototropism?
plant shoots growing towards the light
what experiments were carried out to show how phototropism works?
- shine light from one side onto plant shoots. shoots grow towards the light
- scientists thought this could be controlled by hormones so removed the very tips of shoots and now shoots don’t grow towards the light
- then scientists covered tips with foil to block out the light. now they didn’t grow towards the light
- then used foil to cover lower parts of shoots and they grew towards the light
what did the experiments for phototropism make scientists suggests about plants?
shoot tips produce plant hormones. hormone is called auxin
when shoot tips were covered with foil what did this suggest to scientists?
they are sensitive to light
what did the experiments for phototropism where lower part of shoots covered in foil suggest?
lower parts of shoots aren’t sensitive to light
how do shoots use hormone auxin to grow towards the light?
- auxin produced at tip of shoot and triggers cell growth
- light causes auxin to concentrate on darker side of shoot tip
- auxin spreads down shoot
- cells on darker side grow faster than lighter side
- causes shoot to grow towards light
what is gravitropism or geotropism?
where plant roots grow towards the force of gravity
what does geotropism/ gravitropism involve?
auxin
what happens during geotropism/gravitropism?
- auxin produced in the root
- gravity causes auxin to concentrate on lower side
- auxin in roots inhibits cell growth
- lower side grows slower than upper side causing roots to grow towards force of gravity
what other 2 chemicals to plants use to regulate their behaviour?
giberellins and ethene
what is giberellins useful for?
important in starting the germination of seeds
what does the chemical ethene control?
cell division and ripening of fruits
