1.  Prepare a wet‑mount slide of white onion epidermal tissue. Onions (Allium) have layers of modified leaves (scales – Schuppen) that can easily be separated from one another. Peel off a portion of one layer and examine the concave side of the piece you have obtained. The surface is covered by a thin layer of cells, the epidermis (Epidermis / Abschlussgewebe).

 

2.  Remove a small piece of the epidermis (approximately 3 X 8 mm) by breaking the scale gently, leaving the epidermis intact. Peel the epidermis from one of the halves of the scale. Prepare a wet‑mount slide of the isolated epidermis.

 

3.  Observe the onion cells using low power (10X objective) and then high power (40X objective).

           

4.  If it is difficult to see the cells, add a drop of Lugol's solution (I₂KI) at the edge of the coverslip. The iodine in the Lugol’s solution will stain starch blue/purple.

 

5.  Sketch a representative onion cell as observed under high power, and label its parts.

Which parts are stained by the Lugol’s?

 

Specimen:  ________________________

Magnification: ______________________

Shape and Description: ________________
_______________________________

 

6.  Prepare a wet‑mount slide of red onion epidermal tissue following steps #1-5.

Which differences can you observe? Where does the red colour come from? Where is it stored?

 

 

 

 

 

 

1.      Prepare a wet‑mount slide of an Elodea (Wasserpest) leaf. Observe the thick cell wall, thinner cell membrane, cytoplasm, nucleus, and chloroplasts. A large central vacuole should be apparent.

 

2.      Sketch a representative Elodea cell as observed under high power, and label its parts.

 

Specimen:  ________________________

Magnification: ______________________

Shape and Description: ________________
_______________________________

 

Do the chloroplasts appear to move? Describe their movement.

 

 

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