Cracking Nature's Color-Code for Flowers

Remember the rhyme that begins "Roses are red, violets are blue..."?

Turns out, that's not always the case anymore. Just ask Robert Griesbach. He's a 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, 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 also 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. There, 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.

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.

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.

In case you haven't, click here to learn more about these color-producing pigments.

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

His lab discovered you can change the color of roses, for example, by changing the acidity level or pH of the flower's cells. This helps shuffle around sandwich-like storage forms of flavonoid and other pigments in the cells. So, instead of blood-red, the rose's petals turn blue.

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

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.

— By Jan Suszkiw, Agricultural Research Service, Information Staff

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