Specialised Cells in Amazing African Violets
Introduction
African Violets (Saintpaulia) are native to Tanzania and Kenya.
They are excellent plants for investigating specialised plant cells using a
microscope as you are about to find out.
What you will need:
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African Violet plant – preferably one in flower and with reddish
undersides to the leaves
A sharp scalpel / razor
Microscope slides
Cover slips
A microscope with x4 , x10 and x40 objective lenses
A digital camera or mobile phone with a camera
Safety notes:
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Take care when using scalpels / knives / blades.
Cut in a direction down and away from your fingers.
Glass cover slips are thin and break easily. Handle with care and always
clear away broken glass with a dustpan and brush rather than with your
fingers.
Cells and structures that can be viewed:
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Guard cells and stomata
Hairs (trichomes) and the cells that make trichomes
Trichome contents (and cytoplasmic streaming)
Xylem vessels
Petal Cells
Pollen grains
Science & Plants for Schools: www.saps.org.uk
Amazing African Violets
This document may be photocopied for educational use in any institution taking part in the SAPS programme.
It may not be photocopied for any other purpose. Revised 2012.
First: Take a look at an African Violet leaf
The leaves are covered in hairs called trichomes.
The cells that make up these trichomes are easy to see under a x4 objective lens
Top of the leaf
Underside of the leaf
Here’s how to see some specialised cells on the leaves
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Take some thin slices from the underside of the leaf using a scalpel or a
razor blade.
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Mount the slices on a microscope slide in a drop of water and cover with a
cover slip
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Don’t worry about air bubbles, there will be plenty of other things to see
Science & Plants for Schools: www.saps.org.uk
Amazing African Violets
This document may be photocopied for educational use in any institution taking part in the SAPS programme.
It may not be photocopied for any other purpose. Revised 2012.
What you can expect to see
This image was taken through a x10 objective lens and x10 eye piece using an
standard digital camera held to the eye piece
Trichomes
The hairs on the leaves are made of
several large cylindrical shaped cells. This
trichome is made of 5 cells
Stomata and Guard cells
Guard cells do not have any pink pigment
unlike the cells around them. So they stand
out as white against the pink background.
These yellow arrows above point to two stomata
Close ups of stomata and guard cells
This image below was taken through
the x40 objective lens
You can see the chloroplasts in the
guard cells
Chloroplasts in the guard cells
This image below was taken through
the x40 objective lens with the optical zoom
used on the camera
You can see the chloroplasts in the
guard cells
Bright green chloroplasts
Science & Plants for Schools: www.saps.org.uk
Amazing African Violets
This document may be photocopied for educational use in any institution taking part in the SAPS programme.
It may not be photocopied for any other purpose. Revised 2012.
More about trichomes
In African Violets trichome cells are large. You can see their cells walls and
contents very easily even at low magnifications
These trichome cells were taken down a x40 objective
lens
Things moving inside the cells
Look carefully down the microscope using the x40 objective lens at one
trichome cell.
Keep your eye focused on one part of the cell. Use the fine focus on the
microscope to see grainy particles in the cell. Keep watching – if you are lucky
you will see the particles move around the cell
Once you see this, keep adjusting the fine focus – you may be lucky enough to
see new streams of particles move. Check out the video on the SAPS website if
you want to know what to look for.
Look for movement of grainy particles in the trichome cells
Science & Plants for Schools: www.saps.org.uk
Amazing African Violets
This document may be photocopied for educational use in any institution taking part in the SAPS programme.
It may not be photocopied for any other purpose. Revised 2012.
Xylem
If you take a slice from the underside of a leaf, and across one of the leaf veins,
you may be lucky enough to see some spirals of lignin in xylem vessels
You can also look at xylem in the leaf stalk (petiole)
Both of these images were taken looking down a x40 objective lens
A thin slice was taken along the leaf stalk about 2mm into the tissue.
The microscope needle above is pointing to
a spiral of lignin
Spiral of lignin in xylem
Notice the chloroplasts as well!
Pollen Cells
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Use a scalpel or razor blade to cut open one of the
yellow anthers and sprinkle the pollen into a small
drop of water on a microscope slide
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Cover with a cover slip and look at the cells down a
microscope
Science & Plants for Schools: www.saps.org.uk
Amazing African Violets
This document may be photocopied for educational use in any institution taking part in the SAPS programme.
It may not be photocopied for any other purpose. Revised 2012.
Petal Cells
Look closely at the petals and they seem to shine / be iridescent
Torn thin edge
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Roughly tear a petal so that you obtain some thin tissue where it tears
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This ragged torn edge can be looked at down a microscope
You will be surprised at what you might see
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Trichomes
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Xylem
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Dome-shaped petal cells
Science & Plants for Schools: www.saps.org.uk
Amazing African Violets
This document may be photocopied for educational use in any institution taking part in the SAPS programme.
It may not be photocopied for any other purpose. Revised 2012.
Petal trichomes
This image was taken looking down a x10 objective lens
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Notice that the trichomes have
round ends
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You may also see the cell
contents moving – see the clip
on the SAPS website of the
cell contents moving in the cell
labelled with an arrow
Petal cells
This image was taken looking down a x40 objective lens
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Notice the dome shaped cells
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SAPS learned recently from Dr.
Beverley Glover, Cambridge
University, that this cell shape
could have developed to allow
insects to grip the petal with
their feet more easily
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Notice also the thick cell walls
with iridescence. We also
learned that this could be
because there is a mirror-like
structure to the cell walls
Acknowledgements
This resource was developed by Vicki Cottrell, Nuffield Teaching Fellow 2011-2012, and
a biology teacher at Didcot Girls’ School.
All images by Vicki Cottrell.
Science & Plants for Schools: www.saps.org.uk
Amazing African Violets
This document may be photocopied for educational use in any institution taking part in the SAPS programme.
It may not be photocopied for any other purpose. Revised 2012.