Wednesday, March 5, 2014

The Chemistry of Color

My Tulsa Roses 2013

The Chemistry of Color

Roses are red, and violets are blue, but why? Why do flowers have the colors they have? It's chemistry, specifically pigment molecules.

NBC Learn, the education arm of NBC News, have partnered with the National Science Foundation on a new series, Chemistry Now, which explains the chemistry in everyday life.

"The color is really to make the flower stand out from the rest of the plant so that they will attract insects to spread their pollen," says Dr. Nancy Goroff, a chemist at Stony Brook University.

What determines a flower's coloring is the same thing that decides our own hair and eye color: genetics.  Genes in plant cells direct the production of pigments.

Pigments are chemical compounds that absorb or take in light, especially in the visible rainbow wavelengths we can see.  Here's how it works: whatever colors a specific pigment does not absorb are reflected back into our eye.  That is the color we see.

In flowers, one family of pigments, called carotenoids generally absorb all the light wavelengths except oranges and yellows, which is why we see tiger lilies as orange and daffodils as yellow. Another group of flower pigments, anthocyanins, generally absorb all the light wavelengths except blues and purple, which is why we see those colors in flowers.

Daffodil from our Fredericksburg yard 2014

Dr. Goroff explains, "Sunlight is being absorbed and sunlight is being reflected. We see that difference as color."

For more "Chemistry Now" videos and lesson plans, go to

Bird of Paradise flower from the tropics

Daffodils and other spring-blooming plants are making their appearance already. Our Bradford Pear tree is covered with blossoms in early March. I hope these heralds of spring don't suffer if we have another cold snap.

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