The
Heat

During her more wakeful moments, she edges ever closer to the heater to capture some of its warmth. It's that time of year again, when many species of living creatures, including humans, either hibernate or seek warmth to survive.


is on





Skunk Cabbage

W

ouldn't it be great if we could somehow produce enough warmth within our bodies, so that we wouldn't need to rely on external sources to keep us warm in winter? A strange question perhaps, but one that leads me to the subject at hand: Plants that produce heat.

Lotus Waterlily
(Nelumbonacae)

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Magnolia
(Magnoliales)

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The most-studied plant with this characteristic is the Voodoo Lily (Sauromatum guttatum), aptly named for its magical ability to produce heat. This interesting ability is not well known, perhaps because the foul, rotten-meat odor emanating from its Jack-in-the-Pulpit-like flower is much more obvious. If you can stand the stench and hold the back of your hand close to the flower, you can actually feel the heat. At the peak of its heat production, this lily can heat its flower more than 20 degrees above surrounding temperatures, when those temperatures are around 68 degrees. Even more surprising, at a summertime temperature of, say 95 degrees, the lily can still heat itself to 110 degrees, according to a Science News article titled "Blazing Blossoms."* Other plants that heat up their flowers are Arums (which include Skunk Cabbage), Elephant Foot Yam, several varieties of Philodendron, certain Magnolias, and a few species of Water Lily.

Voodoo Lily (Amorpho-
phallus)

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Cut-leaf Philodendron

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One of the burning and rather obvious questions regarding plant varieties with "hot" flowers is this: What could they possibly gain by heating up their blossoms (especially since some of them are native to the tropics, where it's already hot)? The most plausible theory to date is that the increased temperature of the flower increases the intensity of the fragrance and disperses it over a wider area, thus attracting more pollinators such as insects, birds, and bats. Think of these plants as the world's original candle warmers.

A second obvious question: How do they do it? The answer is that these plants have found a way to switch the respiration in their flowers in such a way that it no longer produces carbon dioxide and oxygen, but rather heat. What is the switch that turns on the heat? Would you believe aspirin?! Actually, it's salicylic acid, which is what aspirin becomes when it's ingested. These plants produce the acid naturally at the appropriate time during their flowering cycles. Interesting, isn't it, that aspirin heats plants up but cools humans down when we have a fever.

What does the future hold for heat-producing plants? In this era of genetic engineering, scientists are already seeking ways to isolate the gene that is responsible for the formation of salicylic acid. Inserted into other plants, it might be able to prevent freeze damage, for example. Perhaps someday we may even choose to fill our homes with heat-producing plants to keep down our heating bills in the winter. Talk about the green revolution! Just kidding. However, some thermogenic plants in the Philodendron family can maintain a temperature of 115 degrees F, which is equivalent to the thermal energy of a domestic cat while sleeping. Another surprise is the fact that the specialized heating tissue in these plants looks--both physically and chemically-- very much like the "brown fat" found in heating tissue of mammals. Perhaps it's not too far out, then, to dream of someday having a greenhouse heated with aroids, philodendrons, and Voodoo Lilies. Now, let's see, how could I keep them blooming all winter...

For the Scientifically-Minded

"Inflorescence of heat-producing plants is accompanied by an extremely powerful increase in respiration, so powerful that it is often called 'metabolic explosion.' This leads to significant heat production, up to 1 W/g of the flower. Due to these intriguing properties, the mitochondria from thermogenic tissues of plants have been intensively investigated. It has been shown that their respiratory activity (in contrast to respiration of mitochondria from non-thermoagenic tissues) is almost completely cyanide-resistant. This fact is connected with increased content of very active, cyanide-resistant alternative oxidase (AltOx). The activity of this enzyme is not coupled with energy conservation; thus, the entire free energy of the ubiquinol-oxidase reaction in thermogenic plant mitochondria is directly converted into heat The activity of AltOx is now believed to be the main mechanism of heat production in plants."

Bertsova, Yu. V., Popov,V. N. and Bogachev, A. V., "NADH Oxidation by Mitochondria from the Thermogenic Plant Arum orientale," ISSN Volume 69, Number 5, May 2004

CREDITS

* Weiss, Rick, "Blazing Blossoms," Science News, June 1989

From DG Plant Files

Skunk Cabbage photo: GardenGuyKin
Skunk Cabbage blossom photo: kniphofia

Waterlily photo: shadowgirl

Voodoo Lily photo: thegreenman66
Voodoo Lily blossom photo: onalee

Philodendron photo: jode

Magnolia photo: Texas A&M University, College Station

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© Larry Rettig 2009