B1g: Controlling plant growth

Growth and development in plants are controlled by plant growth regulators (hormones). This item examines some examples of this, as well as how humans can use plant hormones to aid the efficient production of food. Experiments on seed growth allow the development of safe and accurate working, the presenting of results and evaluation of data collection and the quality of the data. 

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Plants respond to changes in environment. True or false?
True, plants and animals both do.
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What do plant hormones control?
Shoot and root growth, fruit ripening and flowering.
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An experiment to show that shoots grow towards light?
Phototropism.
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How does growth towards light increases the plant’s chance of survival?
Light is needed for photosynthesis, this produces more food, and allows the plant to grow faster.
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Why do roots grow downwards?
They are positively geotropic. There is more auxin on the lower side, the cells on the top elongate faster, so the roots grow down. They are negatively phototropic. The light causes auxin on the shaded side, cell elongation happens here, root down.
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Why are plant hormones used in agriculture?
To speed up or slow down plant growth.
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Describe shoots.
Positively phototropic, negatively geotropic.
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Describe roots.
Positively geotropic, positively phototropic.
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How do auxins move? and what are they responsive to?
Move through solutions. Gravity and light.
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Where is auxin made?
In the tip.
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How are auxins distributed?
Unequally distributed in response to light.
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Why do shoots grow upwards?
The side exposed to less light has more auxin. The cells elongate faster on this side, so shoots grow towards the light, positively phototropic. They are negatively geotropic-gravity distributes an unequal amount of auxin, bottom side elongates more.
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Four commercial uses of plant hormones.
Dormancy, fruit ripening, selective weed killer and rooting powder.
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Explain selective weed killers.
Weeds have broad leaves. Selective weed killers have been to developed from plant growth hormones to only have an effect on broad leaved plants. They disrupt their normal growth patterns, and kill them.
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Explain rooting power.
Normally putting cuttings of plants into soil doesn't make the grown, but using rooting powder, which contains plant hormones, produce roots, and start to grow. This can produce lots of clones of a good plant quickly.
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Explain fruit ripening.
Plant hormones can delay the ripening of fruit. This allows fruit to be picked while its unripe (and firmer, not as easy to damage.) Ripening hormone is then added and the fruit is rip by the time it enters the supermarket.
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Explain dormancy.
Seeds won't germinate until they have been through dormancy. Gibberellin, a hormone, breaks this dormancy and allows the seeds to germinate. This makes plants grow at times they don't normally and seeds in a batch to germinate at the same time.
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Other cards in this set

Card 2

Front

What do plant hormones control?

Back

Shoot and root growth, fruit ripening and flowering.

Card 3

Front

An experiment to show that shoots grow towards light?

Back

Preview of the front of card 3

Card 4

Front

How does growth towards light increases the plant’s chance of survival?

Back

Preview of the front of card 4

Card 5

Front

Why do roots grow downwards?

Back

Preview of the front of card 5
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