A Surprising Carnivorous Plant in British Columbia and the U.S.

Triantha occidentalis is a pretty plant that is carnivorous. (Photo by the US Forest Service, public domain license)

An Interesting Plant Species

Scientists have known about Triantha occidentalis since the nineteenth century. It produces attractive white flowers with yellow stamens and grows in the Pacific Northwest region of North America. Researchers at the University of British Columbia and the University of Wisconsin-Madison have discovered that the species is carnivorous. It doesn’t exhibit the dramatic capture method for insects that a Venus flytrap possesses, but it does trap the animals and extract nourishment from their bodies.

The plant belongs to the family Tofieldiaceae. Its range extends along the coast from Alaska to California. It grows in wild and boggy areas that are low in nutrients but rich in light. The plant has been found near Vancouver in Canada. It has been described as a “part time” carnivore because it only catches insects when it’s flowering. This might sound strange because insects are required to pollinate the flowers. The insects that are trapped are very small and aren’t pollinators, however. In addition, they are caught by the sticky stems of the flowers instead of the flowers themselves. The stickiness of the stems is insufficient to capture bigger insects.

Triantha – a species of false asphodel – is the first new carnivorous plant to be identified by botanists in 20 years. 

UBC Press release

Demonstrating Insect Digestion

Like other plants, Triantha occidentalis (also known as the western false asphodel) contains chlorophyll and carries out photosynthesis. The researchers became interested in the species when they were exploring plant genetics. They discovered that it has a genetic deletion that has also been found in some types of carnivorous plants. When they examined the plant closely, they found that the sticky hairs on the flower stems were trapping small insects such as midges.

In order to prove that the plant was digesting the trapped insects, one of the researchers gave fruit flies food containing a nitrogen-15 isotope. The isotope releases radiation. The researcher then stuck the fruit flies on the flower stems. The insects are tiny and reach a length of about an eighth of an inch. If the plant was capable of digesting the fruit flies and absorbing the products, radiation should have been released from the isotopes that entered its body. Sure enough, the researchers found that radiation was released from inside Triantha occidentalis after the flies had been placed on its flower stems. The amount was comparable to that found in other carnivorous plants that had just eaten a meal of radioactive food. The scientists used non-carnivorous plants as a control group in their experiment in order to demonstrate that the plant’s radiation was coming from the digested insects.

Field experiments, isotopic data, and mixing models demonstrate significant N transfer from prey to Triantha, with an estimated 64% of leaf N obtained from prey capture in previous years, comparable to levels inferred for the cooccurring round-leaved sundew, a recognized carnivore. 

Proceedings of the National Academy of Sciences of the United States of AmericA, or PNAS
Drosera rotundifolia (Photo by Michael Gasperl, CC BY-SA 3.0)

Carnivorous Plant Action

Carnivorous plants don’t engulf their food as we do when we eat. Instead, they release digestive enzymes into their prey. They then absorb the digested products and leave the indigestible husk of the insect prey on the surface of the plant. The scientists investigating the western false asphodel found that its flower stems produced phosphatase, a digestive enzyme. The enzyme is also produced by the sundew and other insectivorous plants. In the other plants, it releases phosphorus from larger chemicals present in the prey. It may do this in Triantha occidentalis as well.

The roundleaf (or round-leaved) sundew (Dosera rotundifolia) is found in the same region as the western false asphodel in the lower mainland region of British Columbia. It’s an interesting plant in its own right. A trip to find both plants would be very interesting, though normal precautions needed during a hike would be necessary, at least where I live.

The researchers warn the plant (Triantha occidentalis) doesn’t do well outside of its natural environment and advise admiring its quirks from a distance.

ubc press release

Understanding the Plant World

Plants seem simpler than animals in many respects. Unlike most animals, they don’t have neurons, or nerve cells, and they lack any structure resembling a brain. Nevertheless, specific signals pass from one part of their body to another, and they are able to respond appropriately to these signals. They are interesting entities that may be more complex than we realize. The behaviour of insectivorous plants is especially interesting to explore because it involves the capture of an organism with a brain (albeit a simple one) by an organism without a brain.

The scientists involved in the research described in this article point out that Triantha occidentalis lives near human habitation, yet we have only recently discovered that it’s carnivorous. There may be other familiar plants in the area that capture animals. The researchers call these plants “cryptic carnivores,” which is an interesting and appealing term. I’m looking forward to seeing what else scientists discover about the behaviour of carnivorous plants and to see whether they soon discover more species in the group.

References

The University of British Columbia press release about the research

Facts about the plant from Flora of North America

The scientific report about the diet of the species from PNAS (Proceedings of the National Academy of Sciences of the United States of America): Significance and Abstract only

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