The advantage of thermogenesis must be strong, because the energy demands on the plant are huge. It is estimated that the skunk cabbage, when maintaining its heat against sub-freezing temperatures, uses as much metabolic energy as a small rodent, or even a hummingbird. Normal plant metabolism is much slower, so this much energy usage is remarkable. In order to generate all this energy, thermogenic plants use an entire alternate respiratory process, one that uses mitochondria and fats, neither of which is involved in normal plant respiration. The whole process, in other words, looks rather more like animal metabolism than normal plant metabolism. This energy cost is undoubtedly why most thermogenic plants don’t maintain heat constantly, but rather use it sparingly. In the arums, only the inflorescence itself heats up, and then only during the day. The skunk cabbage uses heat more lavishly, presumably to protect itself from the cold, but once the snow is gone and blooming is over, it too reverts to normal cold-blooded plant behavior.
Perhaps we should be grateful that plants only use this particular pathway for heat generation. After all, with all that available energy, who knows what they could do by using it for something more than just a little heat. The great monsters of tomorrow may not come from outer space, or the laboratory, but from our backyards.
