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| Seed Growth in Jello |
Answered by: Conrad Richter
Question from: Mary A Whiting
Posted on: March 22, 2007
My son is doing a science fair project related to seed growth. His idea is to place one seed in each of the following mediums: jello, soil, and water; then see which will grow the fastest. He needs to support his hypothesis that the seed in the jello will grow the fastest but we are having a difficult time finding any information related to this. I know this experiment has been done before as last year while helping an older child look for ideas for a Science Fair project, we stumbled across this idea. I can’t recall which internet site we found it at and this year haven’t been able to find it again. Would you happen to know where we would find information related to seed growth that might help to support his hypothesis?
I don’t know the website you are looking for but you may want to try a search with the words "gel and seed germination". Jello is made with gels derived from animal products, but plants also produce gels.
Some herbs are famous for smothering their seeds with a gel when soaked in water. Many varieties of basil do this, and so do some varieties of sage. Probably the best known is the chia sage (Salvia hispanica, S. columbariae) which is used in the "Chia Pet" toys that have been marketed widely in North America over the past few decades. This sage produces copious amounts of gels which sticks to surfaces and seedlings emerge enveloping the "pet" with thousands of tiny bright green leaves. One of the basils Richters sells, Indian basil, is famous in India for its use in a milkshake-like drink called "falooda" and it too produces a gel when soaked to give the drink a wonderful consistency and added nutrition and medicinal value to boot.
I don’t know much about the science behind these seed gels but I suspect that their main role is to provide a stable microenvironment for the seeds during germination and seedling establishment. The seeds release large molecules made up of, among other things, long chain polysaccharides. These long chains are capable of ionizing just like salt in water except that their large size prevents them from dissolving completely like salt, so instead they form a "gel" which may be thought of as a "rigid liquid". A fundamental feature of gels is that water is partially bound or restricted in its movement, and this property is what the seeds are utilizing in order to produce a stable moist environment immediately around each seed during the critical germination period.
It is interesting to speculate why some seeds produce gels while most others don’t. Chia is native to the dry parts of Mexico and the southwestern United States where the rains are few and far between. I can imagine that chia developed this ability to form a gel as a way to seize the opportunity to germinate after a rainfall. The seeds sequester enough moisture in the gel to complete germination until more rain falls in the days ahead. Other plants that don’t have a seed gel may not be able to survive those dry periods between rains, hence chia has a competitive advantage over gel-less species. But because gels require the seeds to release large amounts of scarce resources in the form of these long-chain polysaccharides -- resources that otherwise could be used during the growth and development of the seedlings -- there is a competitive disadvantage to producing these gels, and species that grow where rain is more reliable would be at a competitive disadvantage if they were to produce seed gels. This is probably why most plant species do not produce seed gels. Another possible disadvantage to seed gels may be a greater risk of disease because those long-chain polysaccharides are a favourite food for fungi and bacteria.
Coming back to your child’s experiment, adding Jello probably mimics the effect of seed gels. Adding Jello would give gel-less seeds the same advantage that gel-producing seeds have. So if I were helping my child to do this experiment I would steer the child into thinking about an experimental design that illustrates the role of gels in creating a stable environment for seeds to germinate. I would recommend using smaller seeds instead of larger seeds because smaller seeds are more susceptible to drying out during germination. And I would suggest that the child work out a protocol in which seeds germinating with or without added Jello can be compared. It may take some initial testing to find the best way to do that. To add more real-life relevance to the project your son could even try comparing chia seeds with another seed such as alfalfa in both the added-Jello and Jello-less treatments. If the experiment is set up just right, you son should be able to show that the gel-less seeds fail when no Jello is added and succeed in Jello, while chia succeeds whether or not Jello is added.