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Auxins
Auxins
Auxins control growth of plants by causing cell division and elongation. Tropism is the developed responses to stimuli that promote growth.
Plant hormones control the plant's growth, development of flowers and fruit. Name the hormone that controls growth.
Plants grow in response to light, under the control of auxins. What do we call growth in response to light?
Plants grow in response to gravity, under the control of auxins. What do we call growth in response to gravity?
What happens in full sunlight?
The auxin is produced in the tip and diffuses evenly a little way down the tip. Auxin causes cell elongation, this is how the tip grows in full sunlight.
What happens if there is only light coming from one direction?
The auxin is still produced in the tip and diffuses back a little. But this time diffusion does not happen evenly.
There is more auxin on the...
A) bright side. B) shady side.
The cells elongate more on the...
A) bright side. B) shady side.
What will the auxin then cause to happen when light is only coming from one direction and cells only elongate on the shady side?
A) Plant bends away from the light. B) Plant grows straight up. C) Plant bends towards the light.
Why would a plant want to grow towards the light?
In which direction do most plant roots grow and why?
What is the effect of gravity on the auxin in a root growing sideways in the soil?
It has more auxin on the lower side, caused by gravity.
What happens if a root is exposed to light?
If a root is close enough to the soil surface it may be exposed to a little bit of light, causing more auxin on the lower side (where there is no sunlight).
Auxin has the opposite effect in roots compared to in shoots.
In roots, auxin stops cells elongating!
What is the effect of the auxin in a root?
Due to auxins being on the lower side, lower side cells grow less. As the cells on the upper side grow more compared to the lower side, this causes the root to bend downwards.
What is it in a plant that responds to light and gravity? Pick all the options you think are correct.
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It is the auxin (not the roots or shoots themselves) that responds to sunlight and gravity. Auxin moves away from sunlight into a shady area, and it moves in the direction of gravity to be on a lower side.
In shoots more auxin causes more growth, but in roots more auxin stops growth.
There are many commercial products that contain a chemical very much like auxin. How do you think auxin products can help farmers and gardeners? Pick all the options you think are correct.
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