A new, slimy method of self-pollination

When all else fails for pollination, a yellow flower in the ginger family relies on a substance that botanists say they’ve never seen before: a do-it-yourself oil slick.

Caulokaempferia coenobialis hangs on rock faces in the humid forests of southern China. When Yingqiang Wang of Zhongkai Agrotechnical College in Guangzhou put bags over these flowers to keep wind or insects from delivering pollen, he found that the plants still produced seeds. He and his colleagues didn’t see any insects visiting unbagged flowers in the wild, though they don’t rule out the possibility.

Back in the laboratory, a microscope investigation revealed that in the morning, a drop of pollen-laden oil oozes from the male part of each flower. By midafternoon, the oil has spread to the female flower parts. The flowers sit horizontally, so it’s mostly the spreading property of the oil, not gravity, that does the trick, says coauthor Dianxiang Zhang of the Chinese Academy of Sciences in Guangzhou.

“I have always believed that there are still a lot of unknowns in the tropics waiting to be discovered,” says Zhang.

The scientists describe their findings in the Sept. 2 Nature.