SOME LILIES LIKE IT HOT

by Whit Gibbons

December 30, 2002

A reason given for preserving biodiversity is that we may unwittingly allow a species to be destroyed that has useful, but hidden, properties. A fact now known and accepted by the educated public as well as ecologists is that genes within a species store a unique, complex network of biochemical information. Thus species we know little about may have undisclosed powers that might aid in the cure of human diseases or facilitate the elimination of pests or other agricultural problems.

We do not yet know what powerful attributes the majority of plants and animals hold because we know so little about the basic characteristics of most of the world's organisms. Scientists have not named even half the species that live on earth, let alone unraveled their biological mysteries.

Certain species of lilies serve as outstanding examples of the breadth of unusual qualities found in the plant world. The voodoo lily, with the typical beauty of other members of the group, is a tropical species of Southeast Asia. The voodoo lily has a striking purple flower and reaches a height of almost three feet. A garden lover would be awed by its beauty, but the voodoo lily has another trait that might diminish its popularity in the garden. During the period of pollination, they smell like rotting meat. Associated with this smell is the bizarre phenomenon that the flowers heat up. Temperatures inside a flower in the cool shade can sometimes reach a temperature of 110°F.

Pretty flowers and bad smelling flowers are commonplace, but heat production is generally reserved for members of the animal kingdom. So what is the explanation? The natural history of voodoo lilies is relatively straightforward and might be guessed by someone with a little biological training. Three things to consider about an unusual trait observed in a plant or animal are, how does it enhance feeding, protection, or reproduction? These are the basic essentials for an individual to survive and pass on its genes and are good first considerations for why a plant or animal does what it does.

The most obvious reason for the voodoo lily's thermogenic properties, as they are called, is to attract insects that pollinate the species. Many insects, such as some scarab beetles, are attracted to decaying meat, and the lily flower produces chemicals with such a smell. The added rise in temperature increases the distance from the plant that the smell travels, thus luring insects from afar. In addition, the warm temperatures inside the flower keep the beetles and other insects heated and in an active state, thus insuring maximal contact with the reproductive structures of the flower.

The biochemical explanation is far more complex. Thermogenic plants have been known to science since the 1700s, but only recently have they received sufficient attention for biochemists to begin to understand the physiological processes. In short, the metabolic pathways typical of plants are altered in thermogenic species during reproduction so that instead of storing energy they produce heat. The details are not clearly understood, but one certainty is that voodoo lilies produce salicylic acid during the process. Salicylic acid is the primary pain-relieving agent of aspirin.

Some potential applications of the findings might be the transfer of heat-producing genes to other plants in order to modify their metabolism for various purposes. Perhaps agricultural crops could be produced that are more resistant to freezing or to cold storage. The ability to alter plant metabolic pathways by replacing energy storage with heat production also has promise as a herbicidal agent.

Perhaps the best-known native North American plant species with heat-producing properties is the eastern skunk cabbage. In the Northeast, skunk cabbages are among the earliest plants emerging in the spring, often pushing directly up through a covering of snow that is melted by their generated heat. Some plants have been reported to raise their temperature 45 degrees higher than their environment. One might also suspect that the skunk cabbage, like the voodoo lily, attracts and is pollinated by dead-meat-loving insects, as anyone who has been in their vicinity can attest by the smell. During a season of gift-giving and goodwill, we might do well to remember that such unusual plants may hold great gifts for us that we have not yet opened.



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