LILIES LIKE IT HOT
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
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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