A Hunka, Hunka Burnin' Buds

Saturday, February 01, 1997
Plants, like animals, use oxygen to burn food stored in their cells for energy. In animals this process produces a lot of heat, part of which is used to help maintain a steady body temperature. Being rather sedentary, though, plants generally use less fuel and thus produce much less heat. But Roger Seymour, a zoologist at the University of Adelaide in Australia has found one plant that puts out as much heat as many a more mobile life-form. The sacred lotus, or Nelumbo nucifera, like a warm- blooded animal, can regulate its temperature, keeping its flowers at 86 to 95 degrees even if the air around it is as cool as 41 degrees.

The lotus isn’t the first plant known to elevate its temperature- -in the eighteenth century the French naturalist Jean-Baptiste Lamarck noted the same property in a group of plants known as Arum lilies--but it’s by far the most advanced. The lotus is a much better thermoregulator than any other plant we’ve studied, says Seymour. It’s better than a lot of mammals at maintaining a constant temperature.

Most of the time the lotus behaves like other plants, its temperature fluctuating with the ambient heat, or lack of it. But during its four-day flowering period, Seymour found, the plant changes: its flowers begin to warm up. Seymour discovered this after inserting hair-thin metallic probes attached to a temperature meter into new flower buds and into three different parts of mature flowers--the petals, the stamens, and the receptacle, which houses the plant’s female reproductive parts. He monitored the lotus during its entire flowering period.

The buds’ temperature, initially as low as 55 degrees, soared to an average of 90 degrees and held steady from the beginning to the end of flowering. Eighteen budding lotuses yielded the same result. How the flowers shift into high gear, however, is a mystery.

What does the lotus gain from all this heat output? Botanists have suggested that Arum lilies heat their flowers to better disperse their scent. But Seymour thinks the lotus is catering to the various beetle species that pollinate it. To fly, the beetles must warm up their muscles to about 86 degrees by shivering violently, a process that requires time and energy. By providing heat, N. nucifera may be increasing the efficiency of its pollinators, allowing the beetles to spend more time pollinating and less time shivering.
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