The flowers that line most nursery shelves flaunt petals in what seems like all shades of the rainbow: yellows and whites, pinks and purples, reds and greens. But one color is—like a blue moon—more unusual in the flower world. Now, scientists have discovered what causes some petunias to grow blue petals, rather than the typical red or purple that breed is known for. Blue petunias, they found, have genetic mutations that make two pumps inside the plants’ cells malfunction. The pumps normally ensure that large compartments inside flower petal cells remain about as acidic as a cup of coffee. Without the pumps, these compartments become less acidic and the altered chemical composition of the petals changes the way light reflects off the flowers, giving them their blue hue. The discovery, published online today in Cell Reports, could lead to new ways to engineer other plant breeds, like roses or orchids, to have the elusive blue flowers.
*Correction, 8 January, 12:30 p.m.: The original photo posted was of a morning glory, not a petunia. The photo has now been replaced. Science regrets the error.