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Red onion plasmolysis experiment

Ross Koning koning at ECSUC.CTSTATEU.EDU
Fri Dec 19 14:32:26 EST 1997


At 11:49 AM -0500 12/17/97, Jonathan M. Greenberg wrote:
>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 syru=
p.
>
>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 thi=
s
>work or interfere with it?

Jon,

My 2 cents is use a really high concentration of
sodium chloride rather than sugars...plants take
in and utilize sugars and so they don't work as
planned.  An alternative is to try mannitol.  Finally,
it is really important to either be looking at a cell
at the edge of the piece of epidermis as the solution
can go "around" the piece of tissue and the slide and
coverslip put a really long diffusion pathway to the
center of the epidermal peel.  You can fix that by
floating the peel on the solution and THEN putting on
the cover slip (disadvantage: you cannot SEE the changes
they happen too quickly).

ross


________________________________________________________________
Ross Koning                 | koning at ecsu.ctstateu.edu
Biology Department          | http://koning.ecsu.ctstateu.edu/
Eastern CT State University | phone: 860-465-5327
Willimantic, CT 06226 USA   | fax: 860-465-4479
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