I believe that some plants produce as much heat for their weight as birds do, which are the greatest heat producers of all. It is even harder to believe that some are able to thermoregulate, which means that they actually alter their heat production to keep their temperature constant in fluctuating air temperatures. This is similar to what mammals do. The article I am reviewing tells about few a plants that do this, and how they do it.
There are only three plants which have yet been shown to regulate their temperature. They are the Philodendron selloun, the Skunk Cabbage, and the Sacred Lotus. The most extensive testing has been done on the P. selloun. The earliest testing aimed to do little more than determine whether the inflorescence actually had become hot. In the experiment spadices were impaled with temperature probes into the plant and the probes were connected to a machine that recorded the temperature continuously. During the measurement period the temperature outside averaged 20 degrees Celsius and the temperature in the plant remained 20 degrees higher. This proved that the inflorescence was hotter than its environment.
The next experiment aimed to show the range of the P. selloun's heat producing capabilities. Some specimens were cut and put into indoor cabinets where the temperature could be varied. The reason the plants were placed in indoor cabinets was so that the plants rate of heat production could be measured by the expedient of measuring its rate of consumption of oxygen. Then the inflorescences were examined at air temperatures from low freezing to temperatures that are uncomfortably hot for humans. At the coldest extremes some of the inflorescences could not heat up at all. But their temperatures went to as high as 38 degrees Celsius when the environment temperature was still 4 degrees C. The cuttings became hotter as the air temperature rose further. The inflorescences peaked at 46 degrees C when the inside of the cabinet was 39 degrees C. The plant was adjusting heat production to maintain warmth in cold weather and to prevent overheating in hot conditions. This proved that the plant was indeed thermoregulating.
Past work by others has made a case that plants heat themselves to vaporize scents and attract insects, but this does not explain why heat production is raised and lowered to keep the plant temperature in a certain range. There are two other possible reasons for thermoregulating. One is that it will create a warm, stable environment for pollinators which would facilitate reproduction. Large insects that carry pollen need a high body temperature for flight and often use a great deal of energy to keep warm. So those that land on thermogenic flowers would receive a fairly steady level of heat from the plant. This means that they could eat, digest, and mate while they are on the plants without wasting precious energy to stay warm. The other reason for thermoregulating is that the plant might need heat to develop its own reproductive structures or to protect parts from damage if heat production was uncontrolled.
With these findings I think one day scientists will be able to genetically remove the genes responsible for the thermoregulation in these plants and implant them into other plants, thereby allowing the growing season of plants to be extended which would allow more crops to be grown. Another possibility might be that these plants could be placed next to plants that do not warm themselves which would allow the other plants to survive when the weather got colder.