Module 9. Nutrients

(Level of difficulty ***)

Question: From where do germinating seeds get their nutrients?

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

•Poke small holes (1-3 per container) on the bottom of yogurt containers or cups using an awl (have an adult help you with that!)
•Fill containers with soil and place them in a larger bowl/tray (to capture spills and leaks)
•Pour some water onto the soil to make it moist, but do not overwater (stop watering as soon as you see excess water coming out from the holes onto the tray)
•Put the seeds in soil (it is OK to put multiple seeds into each container, but keep the number of seeds in both containers the same) and cover them with a little bit of soil (finger-thick layer or less)
•Put both containers next to the source of light (a windowsill).
•Wait for 3-14 days for the seeds to germinate
•As soon as the little seedlings come from soil, use small nail scissors to carefully cut off one or both of the embryonic leaves (called cotyledons) taking care not to damage the rest of the plant (ask an adult for help if you are not sure you can do it yourself):
Pot #1 – cut off 1 of the 2 leaves
Pot #2 – cut off both leaves
Pot #3 – leave plants untouched
•Observe further growth of seedlings over time.

Helpful hints and suggestions:
•Don’t forget to label the containers (for example, “no leaves”, “1 leaf”, “2 leaves”), 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.
•Don’t forget to water your plants! The easiest way to water the plants is to add water to the dish/tray your pots are sitting in: the soil and the plant roots will take up the water through the hole that you drilled!

Expected results:

•Plants that had both or one of the two embryonic leaves removed should grow slower than the intact (untouched) plants.
•Dependent on when the leaves were removed and how carefully that was done, plants may not make it and die after the “surgery”.

Follow-up questions:
•Why do you think leaf removal kills or slows down the growth of plants?
•What role do embryonic leaves play? In other words, why do plants need them?
•Which color were the embryonic leaves before you cut them off and why?
•With the embryonic leaves cut off after the seeds have germinated, some plants can still survive, getting their nutrients from the soil and light.  What do you think would happen if you removed the embryonic leaves even before the seeds have sprouted?
•Do you think the results of this experiment would be different if you did the experiment in the dark?
•If you were to repeat the experiment, would you get the same results?
•What would happen if you used another kind of seeds?