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