Onion Cells
Onion Cells - Related Videos
10:39
Bimolecular Fluorescence Complementation (BiFC) Assay for Protein-Protein Interaction in Onion Cells Using the Helios Gene Gun
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Cited by 18 •
2010
This article illustrates how to properly use the BioRad Helios Gene Gun to introduce plasmid DNA into onion epidermal cells and how to test for protein-protein interactions in onion cells based on the principle of Bimolecular Fluorescence Complementation...
06:20
Cell Division - Student Protocol
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2019
Observing the Cell Cycle in a Root Tip ExpandHypotheses: The experimental hypothesis is that in root tips slices that have been treated with nocodazole, a chemical that interferes with microtubular polymerization, all of the cells will be arrested at the same stage of the cell cycle and that in untreated onion tip slices all of the different stages of the cell cycle will be visualized. The null hypothesis is that there will be no differences in mitosis between the two groups and that different...
00:53
Cell Division - Instructor Prep
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2019
Preparation of Onion Root Tips and Solutions ExpandFor the cell cycle experiment using root tips, first, leave an onion suspended over a beaker of water to grow roots for several days. Then, clean the onion roots of any dirt or debris. Next, in a 1.5 mL tube, dissolve 10 mcg of nocodazole per 1 mL of dimethyl sulfoxide solution, making 1 tube per student. Finally, set out all of the other tools, materials, and reagents from the list of materials onto each student's lab bench.
04:51
Cell Structure - Student Protocol
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2019
Visualizing Onion and Human Cells ExpandIn this experiment you will prepare different types of cells from a plant and animal, onion and human respectively, and then visualize them under a microscope. HYPOTHESES: The experimental hypothesis is that the cells will appear different in overall shape and membrane structure, but there will be some shared similar structures, like nuclei, in both cells. The null hypothesis of the experiment is that there will be no difference in structure between the...
01:11
Cell Structure - Instructor Prep
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2019
Visualizing Onion and Cheek Cells ExpandImmediately before the experiment, wash and peel onion bulbs for the class. Remove the entire brown outer skin and cut the onion in half with a knife. Pull apart the layers of the onion. The thin, nearly transparent film layers within the onion will be used by the students. Place the onion film into a Petri dish and then place this into the refrigerator until the students arrive. Bring out the microscopes and set them on the lab bench. Set the microscopes...
FAQs
Iodine or another dye increases contrast between the onion epidermal structures and the surrounding transparent material. Greater contrast helps the cell wall, cell membrane, cytoplasm, nucleus, and central vacuole become easier to identify as light passes through the specimen. This makes staining an important step for connecting a microscope image with recognizable cellular features.
The regular shape of adjacent cells provides a clear outline for locating the cell wall, while the cell membrane, cytoplasm, nucleus, and large central vacuole can be identified within that boundary. Their visibility depends on the prepared specimen, staining, and magnification. Comparing these features helps observers interpret the onion epidermis as an organized group of plant cells.
Viewing the onion epidermis provides direct visual evidence that a living plant structure is organized into repeated cellular units. Students can relate the observed boundaries and internal regions to the broader principle of plant organization. The activity therefore turns an abstract cell-theory concept into a microscope-based observation rather than relying only on diagrams or descriptions.
A thin piece of onion epidermis is placed on a microscope slide, treated with iodine or another dye, and examined with a light microscope. The thin layer allows light to pass through the specimen, while staining improves contrast. During observation, students use the prepared slide to identify cellular structures and relate them to the organization of plant tissue.
These steps provide complementary parts of the observation. A thin epidermal layer creates a specimen through which light can pass, staining increases the contrast of structures, and magnification supports closer examination of the resulting image. Learning to coordinate these elements gives students practical experience with core light-microscopy skills while examining identifiable plant-cell features.
Onion cells provide a simple model for learning how to prepare a slide, apply a stain, use magnification, and recognize cellular structures in a biological specimen. Their large, regular shape and transparent epidermal layer support direct observation with a light microscope. The activity connects practical microscopy skills with plant-cell organization and basic biology instruction.