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SauromGutt.jpg“Hot Plants?”

In the previous post, the topic was how plants survive the cold. Although some perennial plants can withstand winter temperatures well below zero (F), plants certainly don’t generate body heat like mammals do in order to warm themselves.

Or do they?

There are a few plants in nature, like the remarkable Voodoo Lily (Sauromatum guttatum), that produce extraordinary heat when they flower. What actually warms up when the plant flowers is part of the inflorescence, called a spadix.

Typically, the plants do this to attract insect pollinators. But some, such as the Eastern skunk cabbage may actually use this mechanism against the cold.

In the case of the Voodoo Lily, flies are lured by chemical attractants, which are volatilized by the heat of the spadix. (The chemicals smell to us like putrid, rotting meat.)

The process of heat production by living organisms is called thermogenesis. And though it’s far from common in the plant kingdom, thermogenic plants occur in several plant families, especially the Araceae. Members of this plant family include the Eastern skunk cabbage and the giant carrion flower.

Much fewer plants, however, are able to thermoregulate, that is, they actually regulate the temperature of thermogenesis within narrow limits. A nice PDF slideshow of plant thermoregulation can be found HERE (thanks to the Mechanical Engineering department at UC Berkeley).

How Do Plants Generate Heat?

meeuse.jpgMuch about what we know about how the Voodoo Lily spadix, for example, generates heat came from the research of Professor Bastiaan J. D. Meeuse.

Among his discoveries about heat production in plants, Dr. Meeuse and co-workers showed that a compound related to aspirin triggers pronounced heat production in the flowers and inflorescences of some thermogenic plants.

Briefly, heat generation in these plants is due to the massive activation of the alternative oxidase metabolic pathway in the mitochondria inside the plant cells.

Simply put, when this happens, instead of generating ATP as result of metabolizing sugars via oxidative phosphorylation, the mitochondria generate heat.

Bottom line: Though some plants can generate heat to promote flower pollination, it’s unlikely that they do so just to survive cold temperatures.

References

1. Meeuse B.J.D. (1966) The Voodoo Lily. Scientific American vol. 218, pp. 80-88.

2. Meeuse, B.J.D. (1975) Thermogenic Respiration in Aroids. Ann. Rev. Plant Physiology vol. 26, pp. 117-126. (Abstract)

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