Cycad Plant Uses Heat, Odor to Attract Pollinating Insects

Tuesday, March 11, 2008 by: David Gutierrez, staff writer
Tags: plant pollination, health news, Natural News

(NewsTarget) A type of plant that evolved before the dinosaurs uses variations in temperature and scent to trick insects into carrying out pollination for it, according to a study conducted by researchers from the University of Queensland, Australia, and published in the journal "Science."

Researchers studied the Australian Macrozamia cycad, a member in the ancient cycad family. Cycads are tropical and subtropical plants similar in appearance to palms, but actually much older. They are believed to have evolved between 280 and 325 million years ago.

"They reached their heyday during the age of the dinosaurs, but they are older," researcher Irene Terry said.

Unlike the flowering plants that evolved much later and similar to conifers such as pine, cycads reproduce by means of large seed cones. Previously, researchers thought that wind spread pollen from the cones of male plants to the cones of female ones. But according to Terry, the cones of Australian cycads are too tightly closed to allow this kind of pollination.

According to the researchers, Australian cycads instead use a complex system to manipulate insect behavior. First, male cones emit low levels of a scent that attracts flying insects called thrips. The thrips eat inside the cones, covering themselves with pollen as a side effect. After a while, the male cones increase their output of the scent.

Because the scent is attractive to thrips in low concentrations but repellant at higher ones, this drives the insects out of the cones. In addition, the temperature of the male cone increases, rising is high as 25 degrees above the surrounding air, or 100 degrees Fahrenheit.

Eventually, the evicted thrips come across female cones, which are also giving off an attractive scent. Because there is no food inside these cones, however, the thrips leave shortly after entering -- but after the pollen they gathered inside the male cones has brushed off.

"They're luring them in, not giving them any reward," Terry said. "The plants are almost behaving to make the pollinator do what they want."