In Seed Ecology/Seed Science you sometimes need to cut a seed in half — in my case, it was so that we could get it under a microscope or x-ray machine so that we could measure the thickness of its protective seed coat. Cutting seeds in half is also a great way to show students the different parts of a seed, especially if the seeds are stained to improve contrast.

(I suggest a lesson plan based around this seed cutter below, where students compare the germination time of seeds with damaged or intact seed coats.)

Above: A diagram of a wheat seed. (Source)

Cutting seeds in half usually involves holding the seed with pliers while you cut it, but you may crush the seed or lose it. Moreover, very small seeds (1 mm wide) are difficult or impossible to hold with pliers.

This seed cutter makes the process fast and easy.

1. Place a seed into the bowl and tap the cutter on the table. The bowl's elongated shape will cause the seed to align lengthwise.
2. Place a standard scraper blade into the slot. Hold it in the center so that your fingers cover the bowl and prevent the cut seed from flying out.
3. Push the blade down. The seed will be cut near its center line.
4. Invert and tap the cutter on the table to free the seed.

The slot passes through one side of the cutter so that you can push out any debris that settles inside it. The cut seed in the photo gallery is a chive seed measuring 3 x 1 mm (0.118 x 0.039 inch). Even a seed this small was aligned and cut in the correct direction!

No

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The slot was designed to be 0.50 mm wide. On my printer the slot shrinks to 0.35 mm which is perfect for scraper blades, which are 0.25 mm thick. If the slot closes up too much, you can try dunking the print in just-boiled water and then pushing the blade into the slot while the plastic is malleable.

If you must reprint it, try printing slower or reducing your extrusion multiplier/flow rate, or both.

Seeds have a protective coating that can perform a variety of jobs. It can protect seeds from seed-eating insects or other damage, like being crushed by rocks. It can protect the seed from fungal infection. It can stop the seed from drying up, and it can even delay the germination of a seed so that it only grows when conditions are right and it has the best chance of survival, like Australian Acacia spp. and many other plants that only germinate after a fire.

Students will be given seeds from various species of plants, and compare the germination time of seeds that are intact versus seeds whose coats are damaged. By doing this experiment, students can get a practical demonstration of the importance of the seed coat in delaying germination.

This experiment is appropriate for supervised grade school/primary school students. No prior experience is needed.

For each group of students, you will require:

• 3 species of fast-sprouting seeds (Lima beans, zucchini, basil, etc.). Have a look at your local garden center, and 8 seeds from each species. This seed cutter can handle even small seeds!
• Paper towels.
• A seed cutter and blade.
• Two inexpensive take-away containers, one small enough to fit upside-down inside the other with at least a finger-width of space around it.
• Clean water.
• Permanent marker in a colour that is easy to see against the seeds (eg. metallic Sharpie).

1. Scarify half the seeds.

When we scarify (emphasis on scar) seeds, we make a small cut in the seed coat to make it easier for water to get in. Students will use the seed cutter to do this because it is safer than trying to hold the seed any other way.

1. Organise your seeds. For each species, leave half of the seeds undamaged. The other half will be scarified.
2. Place a seed from the scarified treatment into the seed cutter's bowl.
3. Lightly tap the cutter body on the table to make sure the seed is seated properly.
4. Carefully insert the blade into the cutter slot.
5. Lower the blade until it touches the seed, and then tap the spine of the blade firmly with a pen. Do not cut the seed in half. Only penetrate the seed coat.

2. Prepare the water containers

Above: The water containers used for this experiment. The paper towel rests on top of a smaller container, and remains moist by drawing water up from the large container.

You will need 3 water containers, one for each species of seed.

1. Place the small take-away container upside down inside the larger one.
2. Fill the large container with enough water to cover its bottom. Don't add so much water that the small container floats away.
3. Fold a paper towel and place it on top of the small container with its sides hanging down into the water. It will draw up water via capillary action and stay moist.

3. Lay out the seeds

1. Take a water container and place the seeds of one species onto the damp paper towel. Leave a finger-width of space between each seed.
2. Mark the scarified seeds with the permanent marker.
3. Dampen a second paper towel and place it over the seeds, with its sides also dangling into the water.
4. Add more water to the large container if necessary.
5. Repeat 1–3 for the last two species.

4. Monitor the seeds

At the start and end of each day, students will check the seeds. They will record:

1. Time and date of checking.
2. Seed species.
3. Seed treatment (scarified or intact).
4. Germination activity (sprouted or none).

They should add more water to the containers if necessary.

Once all of the seeds have sprouted, students will show their results by making a graph of time points × number of seeds germinated for each species.

1. Did scarified seeds germinate sooner than intact seeds? Why do you think that happened?
2. Was the delay in germination between scarified and intact seeds different between the plant species? Can you list the possible reasons why?

17 Feb 2016

• Added a school project idea using this seed cutter for Thingiverse's MakerEd Project Challenge. Coming up with a reasonable experiment was tricky, so wish me luck!

8 Feb 2016

• Initial release.

https://www.tinkercad.com/things/ltyhfMBC3oy-seed-cutter