Microscopy Image Gallery
Exploration of the Month
August 1998
the flower petals
The sunflower head is also called a composite flower because of the many different types of flowers produced from the same bud. The ray petals on a sunflower are what really make it eye-catching. Besides yellow, they can come in brown and purple colors, depending on the species. They also have a functional purpose: these petals shown can produce a yellow dye. A dye is a chemical which alters the existing color of an object. Most clothes and some foods are created using dyes.
If you look where the stem develops into the head of the flower, another type of petal is visible. These hard, pointy petals are called bracts, indicated by the white arrows. Bracts protect the inside of the flower as the bud is growing. At a certain point in the sunflower's development, the bracts open to reveal the beautiful petals within.
Below are some magnified images of the ray petal. The first picture was taken with the optical microscope. The white bar indicates a distance of one millimeter. You can find this measurement on a common ruler. The next two were taken with the scanning electron microscope. It was interesting to discover the tiny ridges that appeared on the surface of the ray petals. If you have any idea why they look like this, email the address below. All sorts of unexpected images appear when using a microscope!
The next three pictures are samples of the bracts magnified with the SEM. Bracts are rough to the touch just like the leaves and stem. These pictures show why they feel this way. These tiny projections are magnified 10000 times in the final picture. Even at this magnification, you can still see the uneven surface of these little spikes!
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Last Updated: 8/03/98
