AIM: SWBAT explain when stomata are most likely to

be open and why

Please Do Now: Explain how guard cells open and close the stomata in 2-3

sentences

Do Now Data Analysis Stomata notes Lion video

Agenda

Stomata open and close to allow CO2 in for photosynthesis

Remember

They are almost always closed at night

When the plant is very dry and there is not enough water in the soil, they will also close, even if it is sunny out (and could do photosynthesis)

When are stomata most likely to be closed?

When there is an adequate supply of the things plants need for photosynthesis: light and water

In the morning when it is cool out but the sun is shining

Right after a rainstorm when the clouds have passed

When are stomata most likely to be open?

No, the number/density of stomata a plant has is adapted to their particular lifestyle and environment

General trend: more rain = more stomata

General trend: faster growth = more stomata

Do all plants have the same number of stomata?

7

Graph to show stomatal opening over 24 hours

12

2 4 6 8 10

12

2 4 6 8 10 12

stomatal opening/%

0

100

Dawn-stomata begin to open

Increased light intensity causes more stomata to open

Stomata close as the sun sets

Some plants close stomata during hottest time-saving waterAn adaptation to

hot dry environments

Stomata Practice

8

I will now list four scenarios, and you put your thumbs down if you think the stomata will be mostly closed, and thumbs up if they will be open.

Stomata Practice A sunny morning after a soaking rain

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Stomata Practice The middle of a hot afternoon in the middle

of a drought

10

Stomata Practice In the middle of the night after a good

soaking rain

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Stomata Practice Immediately after a thunderstorm

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