Friday, August 3, 2007
Biodiversity Corner: Indian Pipes
On June 29 I wrote about Dodder, a flowering plant with no chlorophyll. Today's topic is another such plant but one with a very different mechanism for acquiring food. Its lack of any green color and its habitat in dark places in the woods, often among mushrooms, cause many people to think it, too, is a fungus of some type, but it is a flowering plant in the same order (Ericales) as rhododendrons, azaleas and blueberries.
Name. Indian Pipes are Monotropa uniflora where Monotropa means one turn or once turned. Young plants have nodding heads that face the ground and as the plant matures the flowers turn until they are looking skyward, making a straight line with the stalk, i.e. the flowers turn once in the lifetime of the plant. Uniflora means one flower and each plant has only a single flower. This plant has many common names including corpse plant, ghost plant, ice plant, ghost pipe, and because of an old-time medicinal use, it has also been called convulsion root.
When and where found. Indian Pipes are common. They are coming up now in the woods all over town. For the most part, head-turning events have not yet occurred in their young lives, so they still have downward-facing flowers.
Distinguishing characteristics. Indian Pipes grow singly and in clusters. They are mainly white although later in the season they are likely to have a pinkish tinge. They blacken as they age. The above-ground part of the stalks is usually around six to eight inches tall. The single flower is carried at the tip of the stalk. Since there is no need for large leafy surfaces to catch the sun for photosynthesis, the leaves are reduced to little white scales that you can see hugging the stalk.
A short digression. A brief explanation of mycorrhizal fungi is needed in order to understand how Indian Pipes get their food. Fungi acquire their food from both dead and living organic matter. Some fungi are wood rotters breaking down cellulose and lignin to sustain their own growth. Mycorrhizal fungi are different. They develop a very close association with the roots of living plants and trees. The particular ones of interest in this case are the ecto-mycorrhizae which coat the outside of the root tips. This is a mutually beneficial relationship in which the fungus makes the plant more vigorous by stimulating root growth and providing access to elemental nutrients. In exchange the fungus gets carbohydrates. Into this mycorrhizal Eden enters the opportunistic Monotropa.
No chlorophyll? No problem. Remember the parasitic Dodder? It wraps its host and uses specialized extraction structures called haustoria to suck out its food. Indian Pipes do not get their food so directly from their host plants. Using a radioactive form of carbon dioxide, scientists have been able to trace the path of carbon from the atmosphere through the tree into the Indian Pipes. They have shown that the mycorrhizal fungi provide the connecting transport system between the tree and the Pipes. The fungi most preferred by Indian Pipes are members of the genus Russula. The Indian Pipe fools the fungus into forming mycorrhizal attachments to it, but this is no symbiotic arrangement. The purpose of the Indian Pipe is only to tap into the nutrients flowing from the tree to the fungus and give nothing in return. The impact of the Indian Pipes' appetite does not appear to be damaging to either the trees or the fungi.
Relatives. Indian Pipes have a close relative called Pinesap, also in the genus Monotropa and also lacking chlorophyll, but each flower stalk has many flowers and the plant usually has some yellow or reddish coloring. Pinesap is not nearly as common in Carlisle as Indian Pipes, but I did see some yellow ones on the Chelmsford side of the Cranberry Bog on July 28.
References. Common Wildflowers of Northeastern United States by Carol H Woodward and Harold W Rickett; Weeds in Winter by Lauren Brown; Mycorrhizal Fungi by Lon Rombough; http://tomvolkfungi.net/ (search for Monotropa).
© 2007 The Carlisle Mosquito