MadSci Network: Botany

Re: How does different liquids effect the germination of bean seeds?

Date: Tue Feb 8 21:10:33 2005
Posted By: David Hershey, Faculty, Botany, NA
Area of science: Botany
ID: 1107879218.Bt

Sounds like you had a well-designed experiment. Seed germination was poor with
skim milk, apple juice and 7up because they contain high concentrations of
sugars. Skim milk also contains high concentrations of sodium salts. High
concentrations of sugars and salts reduce the availablity of water to the seed
or plant. The reduced availability of water can prevent seed germination or
stunt seedling growth.

Softened water has had its calcium and magnesium replaced with sodium. Sodium is
toxic to most plants, however, you said your tap water seedlings looked healthy
so it seems that your softened tap water did not contain enough sodium to
completely prevent germination. Were the tap water seedlings smaller than those
with distilled water or diet cola? Another possibility is that just six seeds
per treatment, maybe you just had lower germination in the tap water treatment
by chance. If your tap water comes from a city water company, you should be able
to get a water quality analysis from the company. That would indicate whether
the water is high in salts or contains other substances harmful to plants.

Distilled water had no salts and no sugar so would seem to be the best treatment
of the bunch. Diet cola had zero sugar, a tiny amount of artificial sweetener
and an unknown amount of salts because the water source used to make it was not
known. Perhaps the water for the diet cola had some mineral nutrients that
benefited the seed/seedling, such as calcium or potassium.

I can't explain the unsweetened Kool Aid treatment. I would expect the Kool Aid
mix to have no effect on plants since it has low levels of salts and no sugar,
just an artificial sweetener and some food dyes. What water did you use to mix
up the Kool Aid? If you used your softened tap water, that may be an explanation.

There are lots of answers about similar experiments in the MadSci archives.
Botanists have not really done such experiments because human beverages are not
usually suitable for plants. It would be very expensive to water plants with
diet soda pop or other human beverage. A better "beverage" for plants would be a
fertilizer solution. 


Hershey, D.R. 1993. Evaluation of irrigation water quality. American Biology
Teacher 55:228-232. 

Re: Why did the liquids kill the plants? Why did the tea do well?

Re: What is a good plant to test the effects of sugar or sweetener?

Re: Why will plants grow in Diet Coke and water and not other sodas?

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