A growth response of a plant towards or away from a stimulus.

Define phototropism .

A growth response towards or away from the direction of light .

Define gravitropism .

A growth response towards or away from the source of gravity .

A plant growth hormone that controls the direction of growth of roots and shoots.

Shoots show a positive response and a negative response, so they grow towards light and upwards.

Shoots show a positive phototropic response and a negative gravitropic response, so they grow towards light and upwards.

Roots grow downwards to anchor the plant, showing a negative response and a positive response.

Roots grow downwards to anchor the plant, showing a negative phototropic response and a positive gravitropic response.

Where in a plant is auxin mostly made?

Auxin is mostly made in the tips of growing shoots and roots.

How does auxin cause a shoot to bend towards light shining from one side?

Auxin concentrates on the shaded side of the shoot. This makes those cells elongate faster, so the shoot bends towards the light.

How does auxin cause a root to bend downwards in response to gravity?

Auxin accumulates on the lower side of the root. Here it inhibits cell elongation, so the lower side grows more slowly and the root bends downwards.

True or False? A clinostat slowly rotates a plant so that all sides receive equal exposure to light.

True. The clinostat cancels out the one-sided effect of light, so the shoot grows straight up instead of bending.

True or False? In roots, a higher concentration of auxin increases the rate of cell elongation.

False. In roots, a higher concentration of auxin inhibits cell elongation, slowing growth on that side.

Why is the gravitropism experiment carried out in a light-proof box?

To cancel out the effect of light , so that only the plant's response to gravity is investigated.

O LevelBiologyCambridge (CIE)Flashcards15. Coordination & Response in Plants15.1 Coordination & Response in Plants

15.1 Coordination & Response in Plants (Cambridge (CIE) O Level Biology): Flashcards

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Define tropism.

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Cards in this collection (12)

Define tropism.
A growth response of a plant towards or away from a stimulus.
Define phototropism.
A growth response towards or away from the direction of light.
Define gravitropism.
A growth response towards or away from the source of gravity.
Define auxin.
A plant growth hormone that controls the direction of growth of roots and shoots.
Shoots show a positive response and a negative response, so they grow towards light and upwards.
Shoots show a positive phototropic response and a negative gravitropic response, so they grow towards light and upwards.
Roots grow downwards to anchor the plant, showing a negative response and a positive response.
Roots grow downwards to anchor the plant, showing a negative phototropic response and a positive gravitropic response.
Where in a plant is auxin mostly made?
Auxin is mostly made in the tips of growing shoots and roots.
How does auxin cause a shoot to bend towards light shining from one side?
Auxin concentrates on the shaded side of the shoot.
This makes those cells elongate faster, so the shoot bends towards the light.
How does auxin cause a root to bend downwards in response to gravity?
Auxin accumulates on the lower side of the root.
Here it inhibits cell elongation, so the lower side grows more slowly and the root bends downwards.
True or False?
A clinostat slowly rotates a plant so that all sides receive equal exposure to light.
True.
The clinostat cancels out the one-sided effect of light, so the shoot grows straight up instead of bending.
True or False?
In roots, a higher concentration of auxin increases the rate of cell elongation.
False.
In roots, a higher concentration of auxin inhibits cell elongation, slowing growth on that side.
Why is the gravitropism experiment carried out in a light-proof box?
To cancel out the effect of light, so that only the plant's response to gravity is investigated.

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