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Explore the building blocks of plants by examining onion cells under a microscope. Observe their rectangular shape, rigid cell walls, and organized arrangement while learning about the structure of plant cells.
Materials
- 1 onion
- Tweezers
- Microscope (compound, 100×–400× magnification)
- Glass slide and coverslip
- Dropper or pipette
- Methylene blue stain
- Paper towel
- Distilled water (dH₂O)
Instructions
- Place one small drop of distilled water (dH₂O) in the center of a clean glass slide. This helps the onion peel stick flat and prevents it from drying out.
- Gently break the onion and use tweezers to lift a thin transparent skin from the inside surface of one onion layer.
- Lay the peel flat on the water drop. Smooth it gently with tweezers so it spreads evenly without folds or air pockets.
- Place one small drop of methylene blue directly on the peel. The stain highlights the nucleus.
- Hold the coverslip at a 45° angle and lower it slowly over the peel to avoid trapping air bubbles.
- Start with the lowest magnification and focus until you see a pattern of rectangular cells. Move to higher power to see more details like the nucleus.
- Draw or photograph what you see, labeling cell wall, cytoplasm, and nucleus.Cell wall: thick, straight borders forming rectangles.Cytoplasm: lighter interior region.Nucleus: small, darker oval inside each cell.
What’s going on?
- The onion’s inner skin is a single layer of plant cells.
- Methylene blue stains the nucleus blue, making it visible.
- The cell wall provides structure, keeping cells rigid and rectangular.
Level
- Intermediate
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