Dr. T. Ombrello - UCC Biology Department

A HOT PHILODENDRON

Common name: Philodendron

Scientific name: Philodendron Selloum

Explanation of scientific name:

Philodendron - from the Greek meaning tree loving, in reference to the climbing ability of the members of this genus.

Selloum - named to commemorate Friedrich Sello (later Sellow) 1789 – 1831, a German traveler in South America.

At home in a tropical rain forest of Southern Brazil, Philodendron Selloum is a huge plant over 8 feet in diameter with broad leaf blades in excess of 2 feet in length. This species is usually found growing on the floor of the rain forest, but it can grow on trees as an epiphyte (a plant that grows upon another and uses it for support but does not derive nutrition from its host) sending long roots down to the ground for water and nutrients.

Most people, however, encounter Philodendron Selloum as a houseplant or even more frequently as part of the interior landscape of an office or lobby. In this environment the plant is considerably smaller than in nature. Its leaves are of the “juvenile” type, either heart-shaped or with a few lobes. The “adult” foliage, finely cut bipinnate (feather-like) leaves, is rarely produced. In addition, a Philodendron Selloum grown indoors almost never flowers. They must be large in size and at least 15 – 20 years old in order to bloom. This may be why, up until recently, the unusual properties of their flowers were not recognized.

Today, the incredible nature of the flowering process in Philodendron Selloum is unfolding. The flower of this species, like other members of the Arum family of plants (Araceae), is a club-shaped stalk with a modified leaf called a spathe partially surrounding it and serving as a hood. Philodendron Selloum flowers are over 1 foot long and contain about 3000 white “florets” on the stalk. The uppermost flowers are fertile males, the lowermost flowers are fertile females, and the middle flowers are sterile males. The sterile male flowers produce heat. This in itself is not too unusual for Arums. Our common native skunk cabbage (Symplocarpus foetidus), whose flowers produce enough heat in the early spring to melt the snow around them, is just one example of a plant liberating heat. What is truly amazing about the flower of the Philodendron Selloum though, is its ability to maintain a constant high temperature. For the 2 days that the flower is open, it maintains a temperature of 114^oF, while the ambient air temperature may fluctuate from 40^oF to 80^oF. The flowers are actually hot to the touch. No other plant on Earth is known to control its temperature, and the mechanism that maintains this is an oddity in the plant world. The sterile male flowers of Philodendron Selloum utilize fat to fuel this energy intensive reaction. This is rare, since plants usually utilize carbohydrates (starches, sugars) for energy. The chemical pathways by which the sterile male flowers use their large reserves of fat for energy are similar to the pathways found in animals. Philodendron Selloum, like most animals, can “burn” fat directly when they need quick energy.

Dr. D. Walker, the discoverer of Philodendron Selloum’s animal-like way of getting energy from fat and maintaining tissue temperature, has said that the species developed the “same strategy of cellular mechanics as did animals. It is an excellent example of convergent evolution whereby two distinct organisms come to the same conclusion because of a similar need”. Dr. Walker has noted that while studying the species’ metabolism (its use of oxygen and food for energy), he made predictions based on what would be expected from a plant. He and his colleagues, however, were constantly surprised to find the plant acted more like an animal. They found its metabolism to “compare favorably with the highest metabolic rate of any vertebrate, including hummingbirds”.

Just why the Philodendron Selloum produces heat as it does remains unanswered but there are a number of hypotheses. In nature, a specific scarab beetle is responsible for the pollination of this species. Somehow the heat must appeal to the insect. The beetles may simply go to the flower to warm up, or they may enjoy mating at high temperatures. Perhaps the heat enhances the release and dispersion of sex attractants from the beetles to lure potential mates. The real answer will require some careful field studies in Brazil. In any case, beetles emerging from the flowers (some are actually trapped by the flowers temporarily as they begin to close) are covered with pollen that will get to other flowers as the beetles make their rounds. This brings about cross-pollination. The ultimate goal of the species is accomplished - reproduction with a good mixture of genetic information for diversity in the next generation.