Onion Root Tip Mitosis Under the Microscope
Onion Root Tip Mitosis (Longitudinal Section), Allium cepa
This is a lengthwise section of an onion root tip stained with iron hematoxylin. It is the classic slide for finding cells in each stage of mitosis, because root tips grow quickly and have many dividing cells.
This longitudinal section of an onion (Allium cepa) root tip is stained with iron hematoxylin, which colors the nuclei and chromosomes dark blue. At the very tip, a root cap of loose cells protects the growing root as it pushes through soil. Just behind it is the meristem, a zone of small, boxy cells that divide quickly. Most cells there are in interphase with a round nucleus, but some show chromosomes in stages of mitosis, such as prophase, metaphase, anaphase, and telophase. Farther back, cells grow longer in the zone of elongation, and students can count how many cells are dividing.
Labeled onion root tip mitosis under the microscope
- Anaphase: Two groups of chromosomes pulling apart
- Prophase: Chromosomes thicken into threads
- Interphase nucleus: Round nucleus, no visible chromosomes
- Metaphase: Chromosomes line up across the middle
What to look for
- Root cap: A cap of cells at the very tip that protects the root as it pushes through soil.
- Interphase cells: Most cells, with a round nucleus and no visible chromosomes.
- Prophase: Cells where chromosomes have thickened into visible threads inside the nucleus.
- Metaphase: Cells with chromosomes lined up across the middle.
- Anaphase: Cells with two groups of chromosomes pulling toward opposite ends.
- Telophase: Cells with two new nuclei forming and a new wall starting between them.
Questions and answers
What does onion root tip mitosis look like under a microscope?
In the region just behind the root cap, you will see many small, square cells. Most are in interphase with a round nucleus, but some show dark chromosomes as threads (prophase), lined up in the middle (metaphase), pulling apart (anaphase), or forming two nuclei (telophase).
Why are most onion root tip cells in interphase?
Cells spend most of their life cycle in interphase, growing and copying their DNA. Mitosis is fairly quick, so at any moment only a small share of cells are caught dividing.
Why use onion root tips to study mitosis?
Root tips grow fast, so they have many dividing cells in one small area. Onion cells also have a small number of large chromosomes (16 in a body cell), which are easy to see when stained.
Compare it
- Category
- Cell Biology
- Scan magnification
- 20x
- Stain
- Iron Hematoxylin
Viewing this slide in class
This is a scan of a real prepared slide, not a simulation or a drawing. On StudyScope you can pan from the whole slide down to individual structures, always in focus, and measure them in real micrometers with the calibrated ruler. Present it live and every student screen follows your view and annotations. Students join with a room code on Chromebooks, iPads, or any browser, with no accounts.