You know that plants need water to survive, just like people and animals do.
But did you ever wonder whether plants sweat, like people do? Well, they don't sweat, exactly, but they do something similar. It's called transpiration, and it's when plants release water through their leaves.
This experiment isn't very difficult, and it's a good way to see some transpiration, firsthand.
What you need to do is break off a piece of a healthy geranium plant. If you're doing this at home, make sure it's okay with the adult in your house. You'll only need a piece of stem and one or two leaves.
Cut out a rectangle about four by six inches from a piece of thin cardboard, such as a shoebox lid. Poke a hole in the middle of the rectangle that's just big -enough for the geranium stem to poke through. Poke the bottom stem through the hole.
Fill a water glass about three-quarters full. Put the cardboard rectangle on top of the water glass, with the stem in the water and the leaf on top of the cardboard. Rub a small amount of Vaseline around the hole. That seals the hole and prevents evaporated water from escaping.
Get a glass that's the same size and type as the first one, and place it upside down over the geranium leaf onto the cardboard. The mouth of one glass should match up with that of the other.
Put the glasses on a bright windowsill and let them sit for at least four hours. Then check out what's happened inside the top glass. You should see little drops of water on the inside of the glass. You know that the water didn't travel up through the hole in the cardboard, because you sealed that off. Look at the underside of the geranium leaf. The little dots you'll see there are called stomates, and they are the source for this water. The water passes through the stem, into the leaf, and what isn't needed is released through the stomates.
