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What is the name of the plant hormone which controls phototropism and gravitropism?
Auxin
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What is phototropism?
The response of a plant to light
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What it is gravitropism (also known as geotropism).
The response of a plant to gravity
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Why are the responses of shoots and roots so important in the life of plants?
To make sure that whichever way up a seed lands, the roots grow down into the soil to anchor the plant and take water and minerals from the soil, and the shoots grow upwards towards the light so they can photosynthesise. This continues to make sure the plant grows to obtain the maximum light
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How can you tell that a plants response is brought about by hormones?
Plants responses are relatively slow, which indicates that they are brought about by hormones
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How can plant hormones be used to kill plants?
They can be used to cause excessive growth that kills plants. They are absorbed more by broadleaved plants that are often weeds rather than by cereals. Hormones can also be used to cause leaf fall, which kills plants as well
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What is auxin?
It's a plant growth hormone that controls growth near tips of shoots and roots
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Where is auxin produced?
In the tips and moves backward to stimulate the cell elongation (enlargement) process which occurs in cells just behind the tips
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What happens if the tip of a shoot is removed?
No auxin is available and the shoot may stop growing
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What heepns when a shoot tip is exposed to light in relation to auxin?
More auxin accumilates in the side that's in the shade then the side that's in the light which makes the cell grow (elongate) faster on the shaded side, so the shoot bends towards the light
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What happens in relation to auxin when a shoot grows sideways, away from gravity?
Gravity produces 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
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What happens to a root in relation to auxin when it's growing sideways?
A root growing sideways will have more auxin on its lower side (because of gravity). But in a root, the extra auxin inhibits growth meaning the cells on top elongate faster and the root bends downwards
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What happens to a root in relation to auxin there's an uneven amount of moisture either side of the root?
An uneven amount of moisture either side of the root produces more auxin no the side with more moisture. This inhibits growth on that side, causing the root to bend in that direction, towards the moisture
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Most weeds in crop fields are......, unlike grasses and cereals which have very......leaves
Broad-leaved, narrow
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What are selective weedkillers made of?
Plant growth hormones
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What type of leaved plant do selective weed killers affect?
Broad-leaved
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How do selective weed-killers work?
They disrupt a plants normal growth patterns which soon kills them, but leaves crops untouched
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What happens if you add rooting powder to plant cuttings?
Rooting powder has auxin in, so the plant cutting will produce roots rapidly and start growing new plants
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Why is using root powder helpful with growing plant cuttings?
It helps growers to produce lots of clones of a good plant very quickly as root powder has auxin in it so it'll produce roots rapidly
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When a stem grows to the left, which side is growing faster?
The right side
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Define tropism
A tropism is a growth in response to a stimulus
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What is positive photropism and what is the part of the plant?
Means that it grows towards the light and this occurs with the shoot
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What is negative photropism and what is the part of the plant?
Means that it grows away from the light and this occurs with the roots
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What is negative gravitropism and what is the part of the plant?
Means that it grows against the force of gravity and occurs with the shoot
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What is positive gravitropism and what is the part of the plant?
Means that it grows in the direction of the force of gravity and occurs with the roots
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