Onion enquiry

This page is dedicated to understanding what happens when an onion begins to grow leaves and photosynthesise. It could be used to explore students’ understanding of cells, respiration, photosynthesis and transpiration and how these important processes work together. Or, it could be used to explore how scientists gather data to generate knowledge about the natural world. Either way, this cheap, safe and intriguing context can provide a platform to ask and answer some interesting questions using important scientific concepts.

The onion enquiry

Take a shop bought red onion and place it in the light until it begins to grow shoots. Once the onion has leaves, students can then decide what they want to investigate. I used a red onion but have no idea if other onions will produce similar results.

the question: what happens to the mass of an onion over time?

the method: an onion was placed on the kitchen table and the mass was recorded every day or so at roughly the same time.  The onion was not given any water.

There was some growth but the mass continued to decrease

The final results are open access

So, it appeared that over a three week period the onion lost mass, although there were a few anomalies along the way. Possibly my kitchen balance needs upgrading. Download results and graph of the onion enquiry.


If you are keen to contribute to our growing understanding of onions please post comments below or share findings on twitter using #onionenquiry. Results will be collated here.

Questions we still need answers to:

  • what happens to onion cells during this period?
  • what dry mass changes take place during this period?
  • how does mass change throughout the day and night?
  • what % of mass lost is due to water loss?
  • what effect does temperature have?
  1. Photosynthesis
  2. Reproduction in plants
  3. Transpiration
  4. Onion enquiry


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