Several tropical plants really turn up the heat when it comes time to procreate, reaching temperatures as high as 105 degrees, a UC Berkeley zoologist has found.
Lloyd Goldwasser, who has studied plants in the forests of Costa Rica since 1980, said the high temperatures are reached during a sexual ritual that attracts beetles that carry pollen great distances so the plants can reproduce.
"The heat volatilizes a chemical that has a pretty strong smell," Goldwasser said in a telephone interview. "Out wafts this odor, and the beetles key in on it."
The odor, which he described as "sweet, but very fresh," is so strong that he could smell it 100 yards away.
"You know for sure if there's one in the neighborhood," he said.
Although scientists have known for some time that the temperature of certain plants rises when it comes time to pollinate, Goldwasser carried the research a step further and studied the plants in their native habitat.
"The main thing that's new (in the study) is how the heating fits in with the ecology of these plants," he said.
He said the plants are members of the philodendron family, and they do their thing at dusk, when the air temperature is 60 to 65 degrees. He said the temperature of the stalk of the plant rises more than 40 degrees in an hour.
This occurred even when he cut a flowering stalk and put it in the refrigerator; the plant's temperature still rose to 105 degrees.
The plants have eight-inch flowering stalks, and during pollination "there is a complete chemical breakdown of a kind of starch into simple compounds," Goldwasser said. "The energy stored in these bonds is released in heat production."
He said the aroma released by the plant attracts beetles that eat some of the flowers before they mate. By around 10 p.m. the stalk cools down to air temperature, and the beetles settle down for the night around the base of the stalk.
The next evening the stalk heats up again, but this time to only about 90 degrees, and the beetles resume dining and cavorting. The result is a bunch of beetles covered inside and out with pollen.
Finally, they fly off to another plant, possibly as far as a mile away, and the ritual resumes.
The process makes reproduction possible for the philodendrons, which grow far apart and have never found procreation easy, Goldwasser said.
He said a philodendron in the wild may grow for several years before one of its flowers gets pollinated.
So, the strong aroma that attracts the beetles from great distances may be nature's way of permitting the survival of the species, he said.