Download Why are stomata important?

Newcastle University – Teacher’s toolkit
Identification of stomatal physiology
Student work book
Introduction
All plants are unique!
Each person on this earth is individual and different. Did you know that plants are too? Each plant species is
unique and each individual plant within that species is unique too, just like you and me!
There are many characteristics that are very important, and are found in all plants. All plant leaves contain a
pore called stomata. These act like a ‘mouth’ and regulate a plants gas exchange and water movement.
The size, shape, abundance and location of the stomata will vary depending on the plant species. Many
plants have stomata on the upper surface and others have stomata on the underside.
Stomata structure
Stomata are made of specialised cells called guard cells and subsidiary cells. There are two guard cells for
each stomata, again think of this as a ‘mouth’ and the guard cells as the ‘lips’. These cells help control
whether the stomata is open or closed. For example, as a plant loses water it will close the stomata to prevent
losing more water, or if a plant needs more carbon dioxide, for photosynthesis, it will open the stomata.
Why are stomata important?
Stomata play an important role in plant homeostasis, which means to maintain a constant internal
environment. Gaseous molecules are exchanged from the plant. Without this pore, no oxygen would be
released from the plant and that means animals would not be able to survive!
Water molecules can also be lost from the stomata by evaporation.
Plant species are adapted to the environment that they live in. Cacti are adapted to hot dry deserts, whereas
water lilies are adapted to living in water.
Why is studying plants important?
Plants are important food sources. By studying plants that can live in certain environments scientists are able
to introduce a gene into another species that is not adapted to that area. The inserted gene causes a change in
the second species and the adaptive characteristic is shown. This process is called genetic engineering.
Subsidiary cell
Stomatal pore
Guard cell
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Photography courtesy of Dr Gordon Beakes
Newcastle University – Teacher’s toolkit
Activity breakdown
Health and safety
Students should:
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Be provided with appropriate PPE
Be responsible with the scissors and nail varnish
Report any breakages or accidents to the teacher
Teachers should ensure that the students are supervised throughout the duration of the activity and should
make sure that there are no students that have allergies to any of the materials being used.
Equipment checklist
Within your group you should have:
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One light microscope
Two pre –set up slides
Two empty slides
Two plant leaves for any plant species
Clear nail varnish
Sticky tape
Scissors
A4 paper
Colourful pens(optional)
Activity 1
Aim: Introduction into microscope use and practice examining slides.
Duration of activity: 20 minutes
Procedure for students
Students should use the provided document ‘Introduction to Microscopy’ to understand how to use a
microscope properly and should examine the pre-prepared slides.
1. Read through the document before starting to examine the slides
2. Set up the microscope and place the slides onto the mechanical stage
3. Practice using the microscope to examine different slides by altering the lighting and magnification
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Photography courtesy of Dr Gordon Beakes
Newcastle University – Teacher’s toolkit
Activity 2
Aim: Preparing a slide and examining stomata
Duration of activity: 30 minutes
Procedure
1. Take a leaf and paint a square patch of clear nail varnish, on the underside of the leaf,
approximately 2cm by 2cm.
2. Allow the patch to dry
3. Carefully use sticky tape to peel off the square and place onto a clean microscope slide
4. The specimen should not need to be stained to allow identification of the stomata
5. Examine this slide and answer the following questions:
Drawing: In the space provided draw a diagram of a stomatal pore including labels and a scale bar.
1. Did you find that the leaves had stomata that varied in shape, size and distribution?
2. Would you expect the stomata on the majority of plants to be open during the night or day?
3. The stomata of a plant will close in response to: high temperature or low temperature?
4. If stomata are open, would you expect more or less photosynthesis to occur?
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Newcastle University – Teacher’s toolkit
Activity 3
Aim: Allow students to apply their knowledge to plant examples and encourage discussion.
Duration of activity: 10 minutes
Procedure:
Within your group divide an A4 sheet of paper down the middle and compare the structure of a cactus plant
and a water lily e.g. leaf size, shape, or photosynthesis rate.
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