pH Testing with Germination
Location: Outside U.S.
Country: United Kingdom
Date: Fall 2010
I am planning an experiment to see whether as a radish
seeds exposure to acid increases, it's germination rate decreases.
In order to ensure the mineral content of whatever I germinate my
seeds in is the same, what would you recommend growing my seeds in,
as using a soil will provide too many variables!
You could grow your radishes hydroponically.
Hydroponics (From the Greek words hydro, water and ponos, labor) is a method
of growing plants using mineral nutrient solutions, in water, without soil.
That way you would have absolute positive control over the content of your
You could try perlite for your seed germination experiment:
Anthony R. Brach, PhD
Missouri Botanical Garden
c/o Harvard University Herbaria
Plants absorb essential nutrients as inorganic ions (positively or
negatively charged atoms or molecules) in water. Soil merely acts as
a reservoir or receptacle for the water and is not directly essential
to the plant’s growth. It is the mineral nutrients in the soil that
dissolve into the plant’s water supply. So in essence all a plant
really needs is mineral-rich water supply.
Hydroponics (Greek for working water) is a method of growing plants
using mineral nutrient solutions in water without soil. Plants may be
grown with their roots directly in the mineral solution or in an inert
medium such as aquarium gravel, marbles or glass pebbles. Hydroponic
solutions allow nutrient levels as well as pH levels to be controlled.
Hydroponic nutrient solutions can be found at local gardening centers
or plant nurseries. Adjusting pH levels in nutrient solutions is
simple. Chemicals such as phosphoric acid (to lower pH) and potassium
hydroxide (to raise pH) are safe and can also be found at gardening
You can obtain thoroughly washed sand from a fish or pet store. Check
the pH of a slurry of sand and water and wash it again with distilled
water. The pH will still be a little on the acid side due to dissolved
CO2, but you can't really avoid that very easily. You can minimize
further absorption of CO2 by keeping the containers covered with
"plastic wrap". You were right on target to avoid using a soil.
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Update: June 2012