Onion Cell Plasmolysis

Using the QX3 Digital Microscope to make Time-Lapse Photography

Anne Bowen

Fall 2002

Overview:

Students use the QX3 Microscope to create still photos, movies, and a time-lapse video of onion epidermal cell plasmolysis in hypertonic salt solution.

Virginia Standards of Learning:

BIO.3 The student will investigate and understand biochemical principles essential for life. Key concepts include

¨ water chemistry and its impact on life processes

BIO.4 The student will investigate and understand relationships between cell structure and function. Key concepts include:

¨ Modeling the cell membrane, cell communication, and cell recognition

BIO.5 The student will investigate and understand life functions of monerans, protists, fungi, plants, and animals, including humans. Key concepts include:

¨ Maintenance of homeostasis

Science Topic:

Water chemistry, homeostasis, lysis, environmental interactions

Materials:

¨ PC with Windows 98 or higher

¨ QX3 microscope

¨ red onion

¨ microscope slides or clear viewing dishes

¨ paper towels

¨ saturated salt solution

Procedure:

T explains the use of the microscope with a projection on the TV screen: focusing, changing powers, adjusting lighting, recording snapshots, movies, and time-lapse videos. Also, show students how the microscope can be removed from its stand.

Ss move to one of four QX3 stations.

Getting Used to the Microscope.

a) Take a penny, and find Mr. Lincoln sitting inside his memorial on 10x and 60x. Take a snapshot of this image on 60x.

b) Take a snapshot of your fast plant flower buds. To do this, remove the microscope from its stand. Your image may be used on the website.

c) Make a movie of someone’s eyeball moving. You must hold the microscope very still to get a clear shot.

Making a time lapse.

1. Peel a thin layer of the red epidermis from a red onion, and place on a slide/dish. Add a drop of water. Adjust microscope light and power as needed. Take snapshot of cells using the camera icon.

2. Dab away water with paper towel, and add a drop of saturated salt solution on the cell peel. Make sure the cells are in focus. Go to time lapse icon, and set the time lapse for 5-second intervals up to 2 minutes.

3. Play back movie to observe response of cell to high-sucrose solution.

Evaluation/Assessment:

Ss will be evaluated formatively as far as participation in this activity. Also, they will be asked to present their recorded shots and videos to the teacher to verify completion.