Hypothesis: If a cross section of a plant’s stem is placed under a microscope, then it would be easier to identify the different structures of the stem.
Materials:
- Microscope
- Microscope slides
- Cover slips
- Bush bean stem
- Microtome
- Melted Parawax
- Scalpel blade
- Petri Plates
- Dish containing 10 mL 50% ethanol
- Dish containing 10 mL 2x Toluidine Blue O stain
- Dish containing 10 mL distilled water
- Small Spatula
- Paper to draw the stem structure
Procedure:
- Obtain and assemble the nut and bolt microtome. Adjust the bolt so that there is a small cup at the end.
- Cut a fresh slice of bush bean stem about 5-6 mm in length. It should be slightly longer than the cup you have formed in the microtome.
- Place the cut stem into the microtome so that it stands up. Using a Pasteur pipet, fi ll the cup with melted parawax provided by your instructor. Work quickly as the parawax will cool and solidify in the pipet.
- Wait 5-10 minutes for the parawax to completely solidify. When the wax has solidified, lay the microtome on its side and with a new single-edged razor or scalpel blade, carefully slice away the excess wax.
- Twist the bolt slightly to expose a thin piece of wax. Carefully slice off a thin section of wax/stem. With this simple apparatus, you are preparing thin cross sections of the bush bean stem. Using a spatula, place the sections in the petri plate containing 50% ethanol. Prepare 10 -12 sections. Allow the sections to soak for 5 minutes.
- Transfer the sections to the Toluidine blue O stain solution contained in another petri plate. Stain for 5-10 minutes.
- Transfer the stained sections to the petri plate containing distilled water.
- Place the sections onto a microscope slide and add a drop of mounting medium or 50% glycerol, and cover with a coverslip.
- Observe the sections under a compound light microscope.
- Make drawings of the structures you observe. Try to see the plant stem cell types.
Photos of the Lab:
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