For this flower, it’s ready, set, launch

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For this flower, it's ready, set, launch

Courtesy of Callin Switzer Flowers are just about the last thing in nature you’d list as fast, but the mountain laurels’ filaments are an exception. The defining characteristic of the flowers, which are native to the eastern United States, is a series of 10 arms or filaments that act like catapults, flinging pollen into the air with startling speed. To understand how those filaments work and why they evolved that way, a team of researchers, including recent Harvard Ph.D. Callin Switzer (now a postdoctoral fellow at the University of Washington), Robin Hopkins, assistant professor of organismic and evolutionary biology at Harvard and a faculty fellow of the Arnold Arboretum, and Stacey Combes, a professor at the University of California, Davis, used high-speed video to determine how fast the filaments move and to show how they target likely pollinators. The study is described in a recent paper in the journal American Naturalist. “Those filaments are under tension, so when an insect comes along and pulls at them, they launch the pollen onto whatever is there,” Switzer said. “There had been two longstanding hypotheses about these catapults. One was that they’re used for wind pollination. But our findings point to the idea that the pollen attaches to pollinators that are likely to take it to another flower.” Those filament catapults are actually long stalks that end with the male part of the plant, called the anther. When the flower develops, the anthers become stuck in tiny pockets on each petal. As the petals open, they pull back on the filaments, increasing the tension on them, and in effect leaving the catapults ready to fire. To understand the speed of those catapults and what they target, Switzer, Hopkins, and Combes conducted four studies.