Flashcards · Biology · The Endocrine System
Plant Hormones
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What is a plant hormone?
A chemical that regulates plant growth and development.
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Where is auxin made?
In the tips of shoots and roots.
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What does auxin do in a shoot?
Makes the cells elongate.
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What is phototropism?
Growth of a plant in response to light.
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What is gravitropism?
Growth of a plant in response to gravity.
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Where does auxin move to in a shoot with light from one side?
To the shaded side.
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Why does a shoot bend towards the light?
Cells on the shaded side elongate more.
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Why does a root bend downwards?
Auxin collects on the lower side and stops the cells elongating, so the upper side grows faster.
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Which hormone breaks the dormancy of seeds?
Gibberellin.
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Which plant hormone is a gas?
Ethene.
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What does ethene do?
Makes fruit ripen.
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What does a selective weedkiller contain?
A synthetic auxin.
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Why is rooting powder used?
Auxin makes cuttings grow roots.
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How can seedless fruit be made?
By spraying unpollinated flowers with auxin.
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Why are bananas ripened with ethene?
They can be picked unripe for transport and then ripened when needed.
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Name the substance shown by the orange dots at X and say what it does. Auxin. It moves to the shaded side of the shoot and makes the cells there elongate more, so the shoot bends towards the light.
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Explain how each plant bends. 
A shoot bends towards light because auxin collects on the shaded side and makes those cells elongate more. A root bends down because auxin collects on its lower side and stops elongation there. A shoot bends up because auxin on its lower side makes it grow more there.