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Plants enjoy hot, smelly sex in the tropics

By Stephen Pincock for ABC Science Online

Posted Fri Oct 5, 2007 11:27pm AEST

It is a relationship characterised by rejection, deceit and too much perfume. An affair played out not on the pages of a gossip magazine, but among Australian insects and plants.

Researchers have discovered that an ancient plant species that grows in south-east Queensland uses its natural scent to manipulate the insects it relies on for pollination.

The plant, called Macrozamia lucida, is a cycad, an ancient group containing species that look part-fern, part-palm, but are in fact related to neither.

Cycads have existed for hundreds of millions of years, since the Permian era, and seem to have an ancient pollination method to match.

This particular Australian cycad can reproduce only with the help of tiny insects called thrips, which in turn rely on cycad pollen for food.

Associate Professor Gimme Walter from the University of Queensland, co-author of a report in today's issue of the journal Science, says the relationship is "very intimate".

"If you take one out of the equation, the other can't manage," he said.

The relationship starts to get complicated around October each year, when the cycads start growing cones to begin their reproductive cycle.

Each plant contains either pollen-containing male cones or female cones, which contain seeds.

Thrips generally set up home among the scales of the male cones. But for pollination, the male plant needs a way to encourage them to make their way to a female.

"It seems that the cycad's got to convince the insect to leave the male cones at some time, and transmit the pollen around," Assoc Prof Walter says.

Sex in the afternoon

In the article, he and his colleagues explain how this happens. It begins between 11am and 3pm each day, when the plants use a stockpile of sugars, starch and fats to heat their cones to around 12 degrees Celsius above air temperature.

"It's quite dramatic, they're hot," Assoc Prof Walter says.

This heating is accompanied by a massive release of scent chemicals from the cones.

In small amounts, their sharp, pungent scent attracts thrips, but repels them at higher concentrations.

Professor Robert Roemer from the University of Utah, a colleague of Assoc Prof Walter, says it is like "a guy with too much aftershave".

MORE AT:-
Plants enjoy hot, smelly sex in the tropics - ABC News (Australian Broadcasting Corporation)