Beautiful Leaves Contribute Form and Function

Mystery: Can you identify what's in this picture? Credit C. Good

What would it be like to have super magnified vision? Imagine you could look at something so closely that you could see it as a group of cells. This mystery picture is a leaf shown as it might look if you used a microscope. Before I go any further, look closely at the picture and describe what you see. (Be sure to use colors, shapes and arrangement in your description.)

Now click on the picture to get a bigger view of the leaf. What do you think the pink layer might be? Tulip leaves, like all leaves, have many cellular layers. These layers have a real special job for the plant.
Have you ever taken a stroll through the tulip garden after it rains? Chances are you would see the plants covered with droplets of rainwater. Did you ever wonder why

Water droplets "ball-up" on outer leaf surface

Careful dissection reveals different layers of the tulip leaf

some plant leaves seem to shed water while others get evenly wet? The bluish color of the leaf tells us that the cells at the leaf surface (the epidermis) have some wax in them. Most plants have wax in their epidermis. The wax is important. It can even act as a kind of sun screen for the leaf!

If you take a look at the shape of the leaf you can clearly see that the shape contributes to repelling water, too. The curved shape and pointed tip act to collect and direct rainwater downward to the soil where the roots can use it.

Journaling Questions

1. How many reasons can you think of that explains why leaves have a waxy outer layer?
2. A tulip's leaf shape is specially designed to direct water to the plant's roots. Can you think of other things that are designed to direct water?
3. How would you set up an experiment to test different kinds of leaves for waxy outer layers?
   

National Science Education Standards

Life Science
Each plant or animal has different structures that serve different functions in growth, survival, reproduction. (K-4)

Living systems at all levels of organization demonstrate the complementary nature of structure and function. (5-8)

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