Plant Responses to Stimuli

​Stimulus and Response in Plants

How Stimuli Affects Growth

Setting up your notebook

These should be folables that flip up and you write the information about them underneath

​Glue the foldables in on pages 42-43 of your notebook

a plant hormone produced in the stem tips and roots, which controls the direction of growth.

Auxin

a growth in response to a stimulus. Plants grow towards sources of water and light, which they need to survive and grow.

Tropism

​Plants need light and water for photosynthesis. They have developed responses called tropisms to help make sure they grow towards sources of light and water.

Write down the definitions above for tropism at the top or bottom of one of your two pages with the foldables. Then watch the video on the next slide.

Write down the stimulus and response for each of your foldables as they appear in this lesson.

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​Your notes

Stimulus: Presence of light

Response: Plant secretes hormones that cause growth towards the light

​Phototropism

Photo=Light

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Watch the video on the next slide to see examples of how and why this happens

Stimulus: Plant comes in contact with another structure

Response: Plant grows around and/or into the other structure for support.

Check out the cool video that shows these "creepy" plants!

Thigmotropism

Thigmo=comes from the Greek for "touch".

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Stimulus: Force of gravity

Response: Roots grow down, shoots grow in opposite direction

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​Some text here about the topic of discussion.

Geotropism/ Gravitropism

Geo=relating to Earth

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​Do try this at home!

Click the link below to see how you can test gravitropism at home with just a baggie, a paper towel, some water and a few dry beans! Germinate the beans by wetting the paper towel and taping the baggie up on a window at home. Observe over several days to see what happens. Be careful not to overwater or they will just get mushy!

Beans in a bag gravitropism lab​

Stimulus: Vacuoles in plant cells fill with water

Response: Turgor Pressure causes plant to become upright.

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​Turgor Pressure

Stimulus: Vacuoles lose water

Response: Plant wilts and cannot remain upright

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Wilt​

Try out the experiment with wilted celery in the next video at home! It's even cooler when you add food coloring to the water!

Stimulus: Darkness, low water supply, and extremes of temperature

Response: closure of stomata and decrease transpiration

Stimulus: light, plenty of water, and optimum temperature

Response: open stomata and increase transpiration.

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​Some text here about the topic of discussion.

Transpiration:

Evaporation of water through the stomata in the leaves

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Stimulus: decreasing temperatures, shortened day length, and/or a reduction in rainfall.

Response: plants begin to move sugars and carbohydrates from the leaves down in the roots to nourish the plant for the winter months. Leaves lose chlorophyll pigment and then fall from the plant.

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​There is no foldable for this so you don't have to write it down, just have an undertsanding of it.

Dormancy​

Stimulus: seed containing stored energy (glucose) receives water and light

Response: turgor pressure and chemical reaction of photosynthesis allows the roots to grow and force their way out of the seed coat and into the ground.

Germination

process by which an organism grows from a seed or similar structure. The most common example of germination is the sprouting of a seedling

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​There is no foldable for this so you don't have to write it down, just have an undertsanding of it.

Multiple Choice

The growth (or response) of a plant towards LIGHT.

• Phototropism

• Thigmotropism

• Geotropism

• Hydrotropism

Multiple Choice

The growth (or response) of a plant towards or away from the Earth’s GRAVITY

• Phototropism

• Thigmotropism

• Geotropism

• Wilting

Multiple Choice

The growth (or response) of a plant towards or away from TOUCH.

• Phototropism

• Thigmotropism

• Geotropism

• Turgor Pressure

Multiple Choice

 

In plant cells, the force, exerted by the flow of water, within the cell that pushes the cell membrane against the cell wall. This force gives plants structure and helps them stand up and not wilt.

• Phototropism

• Thigmotropism

• Geotropism

• Turgor Pressure

Multiple Choice

 

Any change in an organism’s environment that causes the organism to react. Example: The Sun would be this for a plant demonstrating phototropism.

• Stimulus

• Effect

• Force

• Response