Blue roses?

Violets are red, roses are blue,

Soon Japanese chemists may have new flowers for you.

Kumi Yoshida of Sugiyama Jogakuen University in Nagoya and her colleagues have unearthed some mechanisms by which flowers color themselves.

While scientists know that most brilliant flower colors come from the pigment anthocyanin-which, like litmus paper, changes hue when subjected to acids or bases-they had not understood how sap in flower cells controls a petal's acidity.

Yoshida's team inserted a pH-sensitive glass capillary electrode into a flower petal cell of the morning glory, Ipomoea tricolor. Rich in heavenly blue anthocyanin, the flower changes color from a purplish red to a sky blue as it opens.

The scientists found that as a flower opens, its sap grows more alkaline, causing the pigment molecules to change color, they said at last month's meeting of the ICCPBS in Honolulu. In a study of blue dayflowers, cornflowers, and salvia, the researchers also found that metal ions can interact with anthocyanin pigments to stabilize a flower's blue hue, Yoshida told Science News.

Guided by this knowledge, she predicts that genetic engineers may eventually be able to alter the alkalinity of some flower sap cells to yield novel varieties-even a blue rose.