Jonathan,
We use the red epidermis peels from the red onion bulbs, mounted first in
dH2O. Then the students raise the cover slip, blot up most of the water
with a paper towel (without touching the specimen), and add 10% (by wt)
salt (NaCl) solution before replacing the cover slip. We've tried putting
a paper towel at one edge of the cover slip and the salt solution at the
opposite side and drawing the salt solution through but it never works as
well. Maybe the students run out of patience!? After a brief plasmolysis
the procedure can be reversed to return the cells to their normal
appearance.
>We are having trouble with the red onion plamolysis demo, in which a wet
>mount is made of the thin layer of tissue between two layers of a red onion,
>or an epidermal peel from a red layer. Drawing a hypertonic solution in
>under the cover slip form one side with a paper towel on the other is
>supposed to plasmolyze the cells. The red color is supposed to make this
>easil yvisible as the cells contract away from the cell walls. We are not
>seeing any effect, even when using equal voumes of water and dark Karo syrup.
>>Can anyone advise me as to errors in my description above, appropriate
>concentrations of salt or sugar, or any other factor that helps to make this
>work or interfere with it?
>>Many thanks.
>>Jon Greenberg
Dr. David W. Kramer
Department of Plant Biology
Ohio State University at Mansfield
1680 University Drive
Mansfield, OH 44906-1547
(419) 755-4344 FAX: (419) 755-4367
e-mail: kramer.8 at osu.edu
