Sweaty Trees
Just like your body sweats, so do leaves on a tree. Leaves don’t do it to cool
down like we do, but to get rid of extra water. Unless it is very dry leaves
continuously lose water through tiny holes called stomata. This loss of water is
called transpiration. As water is lost from the leaves, it makes a vacuum in the
xylem (like the skin of the tree). This draws more water up from the roots.
Although the plants absorb some of the water they draw up, most of the water
is released back into the air. Here is an activity where you can see transpiration
in action by capturing some of the water lost from a plant indoors or outdoors.
You Will Need:

Plastic bag

Plant, but not one with thick or waxy leaves

String

Water
1. In the morning of a sunny day put a plastic bag over a healthy leaf and tie
the bag tightly shut with string. Be sure not to damage the leaf stem. If
you’re using a houseplant, make sure it is well watered.
2. Let your bag sit until the end of the day.
3. Check your bag. It should have droplets of water in it caused by the
plant’s transpiration.
This activity was adapted from,
Pamela Hickman. The Jumbo Book of Nature Science. Kids Can Press Ltd., Toronto, ON, 1996. Page 79.