Module 7. Water

(Level of difficulty ***)

Question: Is water necessary for plant growth and how much water is right?

Materials you will need:
•5 empty rinsed plastic yogurt containers or single-use cups (any size, preferably 3-10 oz)
•4 larger plastic or Styrofoam trays or bowls
•Soil (dirt from outside should work)
•Seeds (bean, pea, cucumber, tomato, sunflower, corn, pumpkin or squash)
•Water (tap water is fine)
•Plastic wrap

•Fill 4 out of 5 cups with soil and place all 4 in a larger bowl/tray (to capture spills and leaks)
•Using the empty 5th container, pour different amounts of water onto the soil (have an adult help you with the measurements):
one into the 1st pot,
¼ cup into the 2nd pot,
½ cup into the 3rd pot, and
whole cup into the 4th pot
•Excess water will not be able to drain from the cup, so some of the cups will be flooded with water.
•Put the seeds in soil (it is OK to put multiple seeds into each container, but keep the number of seeds in all of your containers the same) and cover them with a little bit of soil (finger-thick layer or less)
•Cover the pots with seeds with some plastic wrap (to keep soil from drying), leaving some space on the top of the container for the seeds to grow
•Put all pots next to the source of light (a windowsill).
•Wait for 3-14 days for the seeds to germinate
•Observe plant growth over time

Helpful hints and suggestions:
•Don’t forget to label the containers (for example “no water” ,“1/4 cup”, “1/2 cup” and “1 cup”), so after your experiment is done you will not get confused which pot is which.
•Dependent on what kind of seeds you planted and how fresh they are, it may take a very different amount of time for the seeds to germinate and grow.

Expected results:
•Seeds in dry soil should not germinate (unless your “no water” pot already had some water, that is if the soil you used was wet to start with).
•Seeds in the pot that was watered with the whole cup of water likely have been flooded and died (unless the experiment was done in a very hot or sunny room and excess water dried up despite of the plastic wrap)
•Usually, ¼ or ½ cup of water would be optimal for the experiment (in other words, the plants should be the happiest with that amount of water) , but the water could have dried up if the experiment was lasting for over a week.

Follow-up questions:
•Why do you think plants need water?
•What do you think would happen to plants if you first germinated them in the presence of water, but then allowed the soil to dry (for example, if you forgot to water the plants)?
•Why do you think flooding kills seeds/plants?
•If you were to repeat the experiment, would you get the same results?
•Do you think the results of your experiment would be different if you did your experiment in the dark?
•What would happen if you used another kind of seeds?