Plant Hormones Flashcards
Phototropism
Plants tendency to grow towards light so they can absorb more for photosynthesis
How did scientists discover whether phototropism was controlled by hormones?
Scientists removed tips of shoots
Then shined light on them
But it didn’t grow towards it
Therefore tips of shoots produce the hormone that causes plants to grow
Auxin
Plant hormone causing growth towards light
How did scientists experiment on plant shoots production of auxin?
Cover the tips with foil
Shine light
It did not grow
Showing tips are SENSITIVE to light
Then cover lower parts of shoots
The shoots grow normally
Therefore lower parts not sensitive to light
How does auxin actually control shoot growth?
Produced in tip of shoot
Triggers cell growth
Light causes the auxin to concentrate on darker side of the shoot
Because it will spread down the shoot on the dark side
Thus it will continue to grow towards the light as more cell growth on dark side
Geotropism/ gravitropism
Tendency of roots to grow towards force of gravity
What controls geotropism?
Auxin again
Where is auxin produced?
The tips of shoots and in roots
How does auxin control geotropism
Produced in roots
Gravity causes it to concentrate on the lower side eg below it
It will INHIBIT cell growth on the lower side unlike in shoots where it triggers cell growth
So lower side grows slower than upper side
Towards force of gravity
Giberellins hormone use
Germination of seeds (into a sprout)
Ethene hormone use
Controls Cell division
Ripening fruits
Gibberellins ethene and auxin uses
Horticulture
Agriculture
Auxin uses
Weed killers
Rooting powder for cuttings (cloning)
Promotes growth in tissue culture (cloning)
Gibberellins uses
End seed dormancy (germinate seeds sooner)
Encourages plants to flower
Makes fruit grow faster
Ethene uses
Food industry:
Where you harvest fruit before ripening
Then store + use ethene to trigger ripening before sold
