Hormones in Plants Flashcards
What is Auxin? What does it control?
Auxin is a plant hormonethat controls growth near thetips of shoots and roots
What does Auxin control the growth of a plant in response to?
Light (photosynthesis)
Gravity (gravitropism or geotropism)
Moisture
Where is Auxin produced?
In the tips
Where does Auxin go after being produced?
It is produced in the tips and then moves backwards to stimulate the cell elongation (enlargement) process which occurs in the cells just behind the tips
What happens if the tip of a plants shoot is removed?
No auxin is avaliable and the shoot may stop growing
Do shoots grow towards or away from light?
Towards
Explain why shoots grow towards light
When a shoot tip is exposed to light, more auxin accumulates on the side that’s in the shade than the side that’s in the light
This makes the cells grow (elongate) faster on the shaded side, so the shoot bends towards the light
Do shoots grow towards or away from gravity?
Away from
Explain why shoots grow away from gravity
When a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side
This causes the lower side to grow faster, bending the shoot upwards
Which ways to roots grow to gravity?
Towards gravity
Explain why roots grow towards gravity
A root growing sideways will also have more auxin on its lower side
But in a root the extra auxin inhibits growth. This means the cells on top elongate faser, and the root bends downwards
Do roots grow towards or away from moisture?
Towards
Explain why roots grow towards moisture?
An uneven amount of moisture either side of a root produces more auxin on the side with more moisture
This inhibits growth on that side, causing the root to bend in that direction, towards the moisture
Are weeds in crop fields broad-leaved or narrow-leaved?
Broad-leaved
Are cereals and grasses broad-leaved or narrow-leaved?
Narrow-leaved
What are selective weed killers made of? What sort of plants do they effect? How do they effect the plant?
They are made of plant growth hormones
They effect broad-leaved plants
They disrupt their normal growth patterms, which soon kills them, but leave the crops untouched (as crops are narrow leaved but this only effects broad leaved)
Explain why adding rooting powder to plant cuttings make them grow?
How is this useful?
Plant cuttings won’t always grow in soil. If you add rooting powder (which contains auxin) they’ll produce roots rapidly and start growing new plants
This helps growers produce lots of clones of a really good plant very quickly
