Warm flowers
We associate warm-bloodedness, or to be more precise the regulation of body temperature through burning nutrients, with animals. With mammals and birds, but not really with plants. There are however, also plants that regulate their temperature independent of their environment. Mostly they do this for a specific organ, for example, their flowers. One of the plant families that is regulating the temperature of their flowers is those of the Amorphophallus, with as most well-known family member the penis plant. But why these plants warm their flowers is unknown. A group of British, Swedish, Swiss, and Israeli scientist made a beginning in answering this question by measuring the temperature regulation of 80 Amorphophallus species.
Characteristic for the flowers of plants of the Amorphophallus family is that their outer leaves form a beaker from a spike is protruding. This spike has a sterile top part, a middle male part with the stamens, and a bottom female part with the ovules. Both the male and the female part are surrounded by the beaker. Earlier researchers noticed that when the plant flowers, the spike heats up.
In order to measure the temperature regulation of the spike, the researchers placed thermometers in each of the three parts of the spike. This allowed the researchers to independently measure the temperature in each part. Which they did for each of the 80 species they studied. They noticed that while the temperature of the sterile and male part of the spike increased during flowering. The temperature of the female part did not.
Long ago the trait of being able to regulate the temperature of their flowers was developed once
The researchers could group the plants roughly in four groups based on the amount of warming. Plants in which the spike temperature did not significantly increase, plants whose spike temperature weakly increased to maximal +2°C, plants that had a clear warming of the spike between +2 and +10°C, and plants whose spike heated up more that +10°C. Most of the measured plants fell in the third group, the so called thermogenic species.
The researchers compared the temperature increases of the Amorphophallus family with their relatedness. From this the researchers could decipher that long ago the trait of being able to regulate the temperature of their flowers was developed once. Later on, multiple species of the family lost this ability again.
Closer examination of what distinguishes the heaters from the non-heaters showed that the heaters often have a thicker and shorter spike. The researchers suggest that this might indicate that beetles pollinate the flowers. The don’t know for sure though, they did not study this. Therefore, it is not jet clear why the studied plants heated their flowers. But with their heat measurements the researchers created a basis from which this can be studied.
Literature
Claudel, C., Loiseau, O., Silvestro, D., Lev-Yadun, S. and Antonelli, A. (2023), Patterns and drivers of heat production in the plant genus Amorphophallus. Plant J, 115: 874-894. https://doi.org/10.1111/tpj.16343
Plant en Zo 