Download What are the Stomata

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Leaf Anatomy: What are the Stomata?
Stomata are microscopic pores found on the under
side of leaves. You will find the stomata in the
epidermal tissue. The stomata are bounded by two
half-moon shaped guard cells that control the width of
the pore. Each guard cell contains chloroplasts. The
glucose concentration of the cells changes with the
photosynthetic activity and therefore it is the guard
cells that regulate the opening and closing of the
stoma.
Stomata under the
microscope
Why do plants have Stomata?
Plants carry on the process of photosynthesis by combining together several
ingredients in their leaves. Some of these materials are gaseous (carbon
dioxide), some are liquid (water), and one is energy (sunlight). If one were to
look at the anatomy of a leaf, it would be easy to see how these materials are
brought to the leaf so that they can form the food. The stomata are the way in
which this transfer of ingredients can occur, transferring the CO2, light and
water from the surrounding atmosphere in to the plant.
In light the guard cells swell, causing the pore to
be at its widest, and CO2 diffuses into the leaf and
into the cells to be assimilated in photosynthesis.
In the dark or under drought conditions the guard
cells are not turgid, the stomata are closed and no
photosynthesis takes place. Opening of the
stomata not only allows CO2 to diffuse into the
leaf, but allows water vapor to diffuse out of the
leaf. The alteration in the size of the stomata
occurs in response to a variety of the external
stimuli such as light, carbon dioxide concentration
and water.
The stomata are situated on the underside of the leaf for the reason that if it
were on the topside the plant would lose too much water. Because the guard
cells are partially light activated, plants under direct sunlight would constantly
have their stomata open and would thus lose much water and the plant dying.
Please define the following terms:
1.
Stomata:__________________________________________________
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2.
Guard Cells:_______________________________________________
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Answer the following questions:
1.
Are stomata open during the day or at night?______________________
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2.
What gases flow into and out of stomata?________________________
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3.
What causes stomata to open?_________________________________
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4.
Can stomata be seen with the naked eye?________________________
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5.
Where on the leaf are stomata located? Why?_____________________
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