Gender-bending flowers spice forests. (Biology).

Ginger flowers switch their working gender--from female to male or vice versa--in unison around lunchtime.

This newly discovered synchronized gender swap in nine species of the genus Alpinia reduces the risk of inbreeding, say Qing-Jun Li of the Chinese Academy of Sciences in Mengla and his colleagues. They report their findings in the March 22 NATURE.

The researchers observed ginger plants in a Yunnan rainforest. Each day, the plants open 2 to 10 flowers, which last only to the end of that day.

Some of the plants start the morning as females with their pollen collector, or stigma, extending downward below male flower parts. In this arrangement, these anthers don't release pollen. At the same time, some of the plants start the day male, with their anthers releasing pollen and their stigmas curled out of the way.

Starting around 11:45 a.m., however, the flowers reconfigure their parts into the alternate pose. By about 2:30 p.m., formerly female blooms open their anthers. Within another 10 minutes or so, the formerly male flowers finish swinging their stigmas down into the receptive position. The exact speed of the midday switch depends on the weather, but the researchers say that a day's sexual shifts are "strictly synchronous."--S.M