Wednesday, July 28, 2010

Fictional botany: Aerophthora repens

Aerophthora repens (air-oaf-THOR-uh REE-penz), also called flor de diablo, flor de silencio, hushvine, orphans' vine, or the obsolete A. bullatus, is the only species in the genus Aerophthora, in the family Aerophthoraceae.

Its natural range is primarily Nicaragua and Costa Rica, with isolated colonies in Panama, Venezuela and Columbia. It is especially common in low-lying areas with rich, organic-heavy, acidic soil, but tolerates a wide range of soils.

The botanical and common names refer to its unique defense mechanism: all parts of the plant, but particularly the leaves, contain hollow, easily broken chambers or tubes in which the poisonous gas carbon monoxide (CO) is stored. (Aerophthora means "corruptor of air;" repens refers to the trailing habit.) No other plant is known to use carbon monoxide defensively in this way. The only analysis performed to date found the concentration of CO within the leaf to be about 90%, with most of the remaining 10% being water vapor and nitrogen.

Because carbon monoxide is colorless and odorless, and the plant typically forms large, thick mats of trailing vines, it is theoretically possible for an invividual to release a lethal concentration of carbon monoxide simply by walking through a field of Aerophthora, given a tailwind and other appropriate weather conditions. No documented cases of such a single fatality are known, however. Aerophthora has, on the other hand, been conclusively shown to kill large groups traveling together, on several occasions. Historians believe, for example, that the plant was a significant obstacle in the Spanish conquest of Nicaragua, in the early sixteenth century. Archaeologists have found large numbers of Spanish weapons and armor, dating to the correct time period, in areas favorable to Aerophthora's growth, and the Spanish log books make reference to multiple unexpected losses of large scouting parties. The culture of the indigenous peoples also include prohibitions on traveling in large groups: though the restrictions do not mention the plant as such (the justification is instead religious, having to do with the number of gods in the local pantheon), it seems reasonable to assume that the danger posed by Aerophthora was the original motivation.

Hushvine is a small, creeping vine with paired round leaves about 1-1.5 inches (2.5-3.8 cm) in diameter, puffed-up or blistered in texture, and typically half as thick as they are wide. New leaves are often slightly reddish, especially in full sun, and hollow; the outer surface encloses a carbon-monoxide-filled chamber which is typically 1/8 inch (3 mm) thick. Leaf color ranges from gray-green to blue-green, usually with a slight iridescent or metallic sheen; this coloration is due to a layer of microscopic bubbles within the leaf tissue itself. These smaller pockets are filled with air, not carbon monoxide, and their purpose is still debated.

Aerophthora produces large, showy flowers in June and July. The five petals are broad and pointed, and lie flat or slightly reflexed. The flowers' overall color is deep blue, with a narrow purple margin on each petal, and in the center, a ring of yellow anthers surround a single white stigma. Flowers range in size from 5 to 8 inches (13-20 cm) in diameter, and last for about 5-10 days. All flowers in a given population bloom synchronously, which is said to be extremely dramatic. Pollination has not been observed, but the pollinator is believed to be a bee. Seed pods are cigar-shaped, nondescript green structures about two inches (5 cm) long which resemble the leaves; they mature in late August or September and split open to release thousands of tiny, windborne seeds. Seeds are viable for three to six months and germinate readily, though they will not develop without full sun and abundant moisture.

The IUCN presently lists Aerophthora as an Endangered species, as it has been the target of aggressive eradication campaigns throughout its range. Though defensively formidable en masse, the plant is easily kept under control through herbicides, the planting of trees (as it cannot survive in dense shade), and hand-pulling of isolated plants. Burning is ineffective, as plants can resprout from the roots. It is presently believed extinct in South America, and present only in extremely remote areas, with low population, in Costa Rica, Panama, and particularly Nicaragua. Though the flowers are very attractive, the plant is not known in cultivation because of the danger it presents.

Though now mostly eradicated, Aerophthora's effects are still sometimes seen in remote areas in the weeks following tropical storms or hurricanes, when weakened trees fall into beds and damage large numbers of leaves simultaneously. The resulting carbon monoxide plume can, depending on the temperature and wind conditions, travel through the forest, killing large numbers of birds, mammals, and other animals before dissipating. This is the origin of the common names "flor de silencio" (silence flower) and "hushflower:" an eerie silence near a field of Aerophthora is a common motif in the legends of the indigenous people.


Paul said...

Should've been an April Fool's entry. Most people don't know CO kills plants, too.

Any chance you'd start scifi botany? Triffids, Elaccawood, Tunyon vine?

mr_subjunctive said...


Are you sure? This site says they just metabolize it to CO2; this site says they both metabolize it and produce it (to the tune of 100 million tons / yr globally), and "there are no reports of these currently measured levels of carbon monoxide producing any adverse effects on plants or microorganisms." This paper (.pdf) says carbon monoxide strongly inhibited cellular respiration in the dark, but the inhibition was reversed when the tissue was illuminated, except for some reason in apples.

I'm seriously asking: I hadn't tried to look this up before writing the post (it had occurred to me to wonder why, with all the plants that use cyanide derivatives for defense, none bothered with CO, but that was as far as the thought process went), so I'm wondering where you got your information from and whether it's really a problem for the post.

Also, if necessary:

Under the microscope, the interior chamber of Aerophthora leaves show themselves to be coated by a unique structure consisting of three layers of dead cells, alternating with four layers of wax with an unusual chemical composition. Scientists speculate that these layers block the migration of CO into the plant's tissues once it has been produced, enabling the 90% concentrations which have been observed.

As for the scifi botany, well, technically this is scifi botany. And it's a lot easier to make stuff up as I go than try to figure out how someone else's plant works.

Liza said...

Huh. Well, I'm confused, but I like the idea of plants killing large groups of people. Makes me want to write a mystery thriller from their perspective.

sigonee said...

Creepy! But I love the name "hushvine." This will make me think twice about stepping on some poor plant while I'm out walking!

Paul said...

"Kills" was probably extreme, but I know any plant surrounded with more CO than CO2 or generic atmosphere will not survive long; light or not. This is probably due to the fact that most sources of CO have multiple other pollutants that mess with plant hormones. The effect on animals is way more profound.

Humans metabolize and excrete CO as well, but that hardly makes it neutral to our biology.

As to why CN (or any other non gaseous toxin) is more prevalent in plants than CO- it's because gasses are difficult to concentrate chemically speaking. It's way easier to accumulate and store liquids.

A problem? The only problem I see is a 1954 abstract. As for your plan, it's fictional botany, so you can make up whatever you want.