Module 4. Temperature

(Level of difficulty **)

Question: How does temperature of the environment affect plant growth?

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

•Poke small holes (1-3 per container) on the bottom of 2 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)
•Wrap containers with foil (it will block the light and keep the plants in the dark), leaving some space on the top of the container for the seeds to grow
•Place each one of the cups in a tupperware and seal them (this will avoid any spill inside the refrigerator. Place one cup in refrigerator and leave another one at root temperature.
•Wait for 3-14 days for the seeds to germinate
•Observe plant growth over time and examine how plants look after, for example,  5,10, 15, and 20 days after planting.

Helpful hints and suggestions:
•Don’t forget to label the containers (for example “cold” and “warm”), 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. You can use a non-covered cup to estimate how long does it take to your seeds to germinate (we should put this in most cases above).
•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:
•Seeds in the cold are likely to germinate significantly later than at room temperature.
•The cold-grown seeds may not germinate at all in the course of this experiment.

Follow-up questions:
•Why do you think cold-grown plants develop so much slower than the room temperature ones?
•Do you think the outcome of the experiment would be different or the same if plants had been grown in the light?
•What do you think would happen with your plants if you continued to grow them in the cold: would they eventually germinate and catch up?
•What would happen if you moved cold-grown seedlings to room temperature?
•If you were to repeat the experiment, would you get the same results?
•What would happen if you used another kind of seeds?
•Do you think it is good for a seed in the forest to germinate during the cold winter?