Flashcards · Biology · Plant Adaptations and Hormones
Plant Hormones and Tropisms
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What is a plant hormone?
A chemical that controls and coordinates growth and development in a plant.
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Where is auxin made?
In the tips of the shoots and roots.
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What does auxin do in a shoot?
Makes the cells elongate.
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What is a tropism?
A growth response to a stimulus from one direction.
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What is phototropism?
Growth in response to the direction of light.
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Where does auxin go in phototropism?
To the shaded side of the shoot.
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What happens to the shaded side of a shoot?
The cells elongate more, so the shoot bends towards the light.
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What is gravitropism?
Growth in response to gravity.
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Where does auxin collect in a shoot on its side?
On the lower side.
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Why does the shoot bend up?
The lower side grows faster.
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Why does the root bend down?
Auxin on the lower side slows its growth, so the upper side grows faster.
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What is positive phototropism?
Growth towards the light.
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Why is phototropism useful?
The leaves receive more light for photosynthesis.
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Why is gravitropism useful in a root?
It grows down to find water and to anchor the plant.
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What did Darwin show?
The tip detects light, as shoots with covered tips did not bend.
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Common mistake about auxin?
Saying that auxin makes the lit side grow. It moves to the shaded side.