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In the second part of the lab we were instructed to observe onion membrane cells. We took a small piece of membrane, placed it on a slide, applied some distilled water and looked at the specimen under the microscope.

We saw clear, rectangular cells with a light green border.

We then applied 1% NaCl and observed the result.

The cell membranes appeared to dissolve, drying out because of the NaCl. The light green border disappeared, leaving a faint gray outline of the cell, and an ugly shrunken form in the center.

Our explanation: the cells were dried out from the NaCl; the water moved out of the cell as the 1% NaCl was drawn into the slide. (The cells wanted to reach equilibrium with their environment, i.e. balancing the concentration of water and NaCl). As a result the cell membranes grew flaccid and shrank while the cell walls remained the same.

Questions: what would happen if you were to apply dye instead of 1% NaCl? Would you be able to observe the absorption of one substance and the expulsion of water? Does this experiment work on other plant cells?