US National Arboretum


Floral and Nursery Plants Research Unit

Cracking Nature's Color-Code for Flowers

Animated flower image turning blue to red. Remember the rhyme that begins "Roses are red, violets are blue..."?

Turns out, that may not always the case anymore. Just ask Robert Griesbach, a research plant geneticist at the ARS Floral and Nursery Plants Unit, located in Beltsville, Maryland.

There, Griesbach and other plant scientists are writing a new nursery rhyme, setting the stage for creating roses that are blue, not red.

New advances in science are making it possible to change the natural colors of many flowers--not just roses. Griesbach's lab, for example, has created orange petunias, a new, "high-tech" variety you're not likely to spy in the flower garden.

That's because the scientists plucked a gene from corn plants and stuck it in the petunia's cells. [Gene: a segment or region along a twisting strand of DNA, or deoxyribonucleic acid.  Genes are perhaps best known for their role in deciding the traits, or features of an organism, such as blue, brown or hazel-colored eyes in people, orflower color in plants]. Once in the petunia cells, the corn gene works like a chemical switch. "It tells the flower how to make a new pigment for orange-colored petals instead of blue ones," explains Griesbach.  [Pigment: In plants, pigments are natural substances that add color to stems, leaves, flowers and other parts.  There are many different types of plant pigments].

But why stop at just orange or blue? What about a rainbow of colors for flowers like roses, which are normally either red, yellow, pink or a creamy white?  Imagine handing a bouquet like that to your mom on her birthday. She'd flip! 

Rainbow-colored roses sound impossible? Not really, says Griesbach.

Patent-pending Ornithogalums The trick is to find the right genes and mix just the right amounts of three funky-sounding pigments. One is called flavonoids (they've got nothing to do with flavor). Another is carotenoid and a third is chlorophyll, which you've probably heard of. Animated drawing of a carotenoid-containing sunflower moving up and down.

[In case you haven't - - Color-producing pigments include the following: 
The first, Flavonoids, are quite common in roses. They produce red through blue colors.
Carotenoids, found in sunflowers and marigolds, produce yellow and orange coloring. 
Chlorophyll, the third pigment, gives plants their green color].

"By mixing and matching these three pigments," says Griesbach, "an endless array of colors can be created."

His lab also discovered that you can change the color of a flower, for example, by changing the acidity level (or pH) of the flower's cells. A change in the acidity level of a cell or soil, for that matter, can trigger pigment color changes in certain flowers like petunias and morning glories. Catch this last flower early in the morning, and you'll notice that its buds are bright pink. But in the afternoon, after they've opened, the petals are a pale blue.

So, with a change in pH in the rose flower cell - interacting with the rose flower cell flavonoids  - instead of being blood-red, the rose's petals will turn blue.

Griesbach says sticking genes from one flower or plant into another could create a new palette of splashy colors to choose from.

Animated drawing of a flower with its petals opening and closing. If Mom likes to grow her own flowers, for example, this would give her more of a choice in where or when to plant her very favorite varieties.

Animated drawing of glowing blue flowers. Animated flower image turning blue to red. Animated drawing of glowing blue flowers. Animated flower image turning blue to red. Animated drawing of glowing blue flowers

This page was adapted from an article by Jan Suszkiw, (Information Staff, Agricultural Research Service) for USDA's Sci4Kids.
Be sure to visit Sci4Kids home for other USDA Research Articles of interest to students.

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Last Updated   January 18, 2005 4:30 PM

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