LINKS TO AUSTRALIAN CURRICULUM Year 8: Science Understanding, ACSSU149, ACSSU150: Science Inquiry Skills, ACSIS149; Seniorsecondary curriculum: Biology Unit 2, Science Inquiry Skills, ACSBL032.
BACKGROUND
METHOD 1. Set aside a clean microscope slide.
2. Carefully cut away a small, single layered piece of onion (1-2 cm
wide).
3. Peel the thin layer of skin
(membrane) from the inside
surface of your piece of onion.
Forceps may help with this. The
membrane looks a bit like soft
Scotch tape and should separate
relatively easily from the inside
surface of the onion slice.
TO DISCUSS Chloroplasts, responsible for
photosynthesis, are only present
in the leafy part of the onion
(above ground) and absent in the
bulb (which grows below ground).
Why might this be?
VIEWING PLANT CELLS UNDER THE MICROSCOPE: onion cell preparation
This method allows students to view plant cells under the microscope. A single layer of onion cells (membrane) can be easily obtained from the bulb. These can be stained to bring some cell structures - including the nucleus and cell membrane/wall - into contrast, so that they can be observed using a light microscope.
• Onion • Knife • Forceps • Glass microscope slides • Cover slides • Iodine solution • Pipette/dropper • Microscope • Paper towels
You need:
4. Place section of membrane carefully on the microscope slide, trying to keep it as flat as possible.
5. Apply a couple of drops of iodine solution to the section. Wait 2 minutes for the stain to develop
before positioning a cover slip over the section.
6. Place the slide under 40x magnifying lens and observe the onion cells.
*note: Be careful, when focusing the microscope, not to break the glass slide with the microscope lens.
Onion (plant) cells
Nucleus
Cell wall/cell membrane
Cytoplasm
CC 2.0 kaibara87
Document prepared by the ARC Centreof Excellence in Plant Energy Biology (V1)
METHOD 1. Set aside a clean microscope slide.
2. Carefully cut away a small, single layered piece of
onion (1-2 cm wide).
3. Peel the thin layer of skin (membrane) from the inside
surface of your piece of onion. Forceps may help with
this. The membrane looks a bit like soft Scotch tape and
should separate relatively easily from the inside
surface of the onion slice.
4. Place section of membrane carefully on the microscope
slide, trying to keep it as flat as possible.
VIEWING PLANT CELLS UNDER THE MICROSCOPE: onion cell preparation
Student sheet
Document prepared by the ARC Centre of Excellence in Plant Energy Biology (V1).
• Onion • Knife • Forceps • Glass microscope slides • Cover slides • Iodine solution • Pipette/dropper • Microscope • Paper towels
You need:
5. Apply a couple of drops of iodine solution to the section. Wait 2 minutes for the
stain to develop before positioning a cover slip over the section.
6. Place the slide under 40x magnifying lens and observe the onion cells.
*note: Be careful, when focusing the microscope, not to break the glass slide with the
microscope lens.
Onion (plant) cells
Nucleus
Cell wall/cell membrane
Cytoplasm
CC 2.0 kaibara87