1. ONION CELLS

2. ONION PLANT
This is what a whole
onion plant looks
like.
We will be looking at
cells from the onion
bulb.
The bulb is the
storage tissue of the
whole plant.

3. Copy CELL WALL
Plant cells have cell walls.
• Cell walls are made up of cellulose.
• They protect the cell.
• Maintains the cells shape.
• Prevents excessive water uptake.
When staining your onion cell, you will need to wait a
minute or two before viewing it under the microscope.
The stain can take some time to sink in to the cells
because of the barrier that the cell wall creates.

4. CHLOROPLASTS
Are a specialised organelle that
is the site for photosynthesis.
Photosynthesis is a chemical process that
captures light energy and transfers it into
useful chemical energy.
Because photosynthesis requires
light, chloroplasts are mainly found in cells
of leaves and stems (parts that are
exposed to more sunlight).

5. Do onion cells have chloroplasts?
Onion cells do not have chloroplasts because
the onion is underground (where there is no
light).
Without light, chloroplasts have no purpose.
The green leaves and stem of an onion plant
are normally exposed to daylight and so have
chloroplasts, but the onion does not.

6. INTERLOCKING CELLS
Interlocking of cells gives small, thin
structures (like leaves) a large amount of
strength.

7. STARCH
GRANULES
Because the bulbs are the storage tissue
of the plant, you might see some starch
granules in the slide that you create.
Starch granules are small spheres that
store excess starch. Starch is made
from many glucose molecules joined
together. Glucose is the energy
molecule made by photosynthesis.

8. PREPARING
SLIDES
• The torn tissue used must be thin (sliced
or torn)
• The tissue must be flat on the side
• Add a few drops of stain
• Slowly lower coverslip so there are no
air bubbles

9. Copy STAINS
• Animal cells are best stained with
Methylene blue as it shows the nucleus
well.
• Plant cells are best stained with Iodine as
it shows the cell wall and nucleus well.
• A wet mount is made using water
• The stain should be just under the
coverslip (not everywhere)