Onion root cells school experiment with the 3D Cell Explorer and software STEVE – a step-by-step guide

cell.academy invites students to discover the basic unit of life as it is, alive and in motion, and to live a true scientific experience. 

This demonstration will show you how we prepare a wet mount of onion root cells which will then be observed under the 3D Cell Explorer microscope. This data is then uploaded to the Learning Space where students can interact with it using the software STEVE – a 3D/4D Interactive Cell Viewer – to identify the cellular structures in an onion cell and distinguish the different stages of mitosis. cell.academy is the ideal tool to inspire students to become the scientists of tomorrow!

1) Hands-on experiment

All data on the Learning Space are of real cell images taken with the 3D Cell Explorer microscope. The video demonstrates how we prepared an onion root-tip squash to observe different stages of mitosis.

2) Image visualization

The software STEVE has an integrated cloud platform where you can find all the cell data and worksheets. You can explore the raw cell data on the left and get an automatic 3D render of the cell on the right. The video shows how to log-in to the Learning Space and open the .vol file of onion mitosis in the Cell Database Cloud.

3) Digital staining

The 3D data is presented as a map of the refractive index of the different parts of the cell. With STEVE, students can easily add colours to highlight the different structures in the colours of their choice – creating their own beautiful cell images. In the video we show you how to add digital staining to highlight the chromosomes.

4) Exploration and understanding

The worksheets provided on the Learning Space guide the students through the exploration of the cells. The questions on the worksheets point the students in the right direction for them to understand dynamic cell processes. Here are a couple of examples:

  • Which stage of mitosis is this cell in?

Anaphase, the stage during which the chromatids move away from one another to opposite poles of the spindle.

  • How many chromosomes does an onion cell have?

You can see 16 chromosome tips in the 3D view, therefore there are 16/2 = 8 chromosomes in an onion cell. Remember that during anaphase, the chromatids are pulled from their center.

5) Problem solving

The worksheets on the Learning Space also include quantitative questions which require using STEVE to measure cell size and volume, then to proceed with unit conversion to understand and put in context the size of cells.

For example:

Considering that you cut off 1 cm of your initial root-tip, on average, how many onion cells are aligned in this 1 cm preparation?“

  • Choose 6 different onion cells and use the ruler tool in STEVE to measure their length.

Cell 1: 38.7 µm                   Cell 5: 30.2 µm
Cell 2: 40.7 µm                  Cell 6: 29.2 µm
Cell 3: 25.4 µm                  Cell 7: 36.9 µm
Cell 4: 37.3 µm                  Cell 8: 32.3 µm

  • Calculate the average value of the length of an onion cell.

(38.7 + 40.7 + 25.4 + 37.3 + 30.2 + 29.2 + 36.9 + 32.3) / 8 = 33.8 µm

  • Divide the length of the root tip by the average length of an onion cell to get the number of cells aligned in this root tip.

1 cm = 10000 µm
Length of root rip/Average length of onion cell = number of cells aligned in the root tip.
10000 µm / 33.8 µm
296 cells

Video Demonstration

Watch the complete demonstration as a video!