Welcome to Mushroom Monday for April 2, 2018
Posted by Gary Hunt
And welcome also to the new website of the Kamloops Naturalist Club. I hope you return often to see the wide variety of nature-related activities our members are involved in.
There is a group of wildflowers that have learned how to cheat photosynthesis. This allows them to simplify physical structure and eliminate the work of making chlorophyll and their own food. It confers a significant survival advantage in low-light forest conditions.
Chlorophyll is what makes our familiar plants green. We call them autotrophs (“self-feeding”), meaning they make their own food from sunlight, water, and carbon dioxide. There is a fascinating group of flowering plants that have evolved away from autotrophy. They have no chlorophyll (or almost none) and leaves are absent or greatly reduced in size. These are heterotrophs (“other-feeding”) and they must obtain nutrition from other organisms. They are not saprophytes because their nutrition does not come from decaying organic matter.
There are two groups of heterotrophic plants. One group is called haustorial parasites. In this group, modified roots called haustoria, fuse directly to the root system of a host tree and fungi are not involved in nutrient acquisition. Haustorial parasites include members of the Broomrape family (Orobanchaceae). Examples are ground cone (Boshniakia strobilacea), California broomrape (Orobanche californica), and squawroot (Conopholis americana). California broomrape occurs in BC. It arises from a thick root system and gets to about 35 cm tall. It has no chlorophyll or leaves. The tubular flowers produce a capsule fruit.
The second group of heterotrophic plants are mycoheterotrophs. They obtain their nutrition from a host green plant through an intermediary mycorrhizal (symbiotic) fungus. Through a chemical recognition system that is not understood, they tap into an established mycorrhizal association between a tree and fungus. With few exceptions, mycoheterotrophic species are specialized to certain families, genera, or species of fungus. Some are so specialized that their seeds will not germinate unless the proper fungus is present. This mode of nutrient acquisition has evolved many times in plants and includes some mosses and ferns. Over 450 plant species are fully mycoheterotrophic and lack chlorophyll completely.
In North America, the majority of mycoheterotrophic species belong to the largest family of flowering plants, the orchids (Orchidaceae) or the heath family (Ericaceae). In the Southern Interior, we have the striped coralroot (Corallorhiza striata) in the orchid family, one of our three species of coralroot orchids. Our Ericaceous examples include the Indian pipe or ghost plant (Monotropa uniflora) and pinedrops (Pterospora andromedea).
Striped coralroot takes its name from stripes on the flower parts. It blooms in spring and summer and occurs in mid and low elevation moist shady forests.
Indian pipe is the most common mycoheterotroph in our region. The stems reach heights of 10–30 cm and have small scale-like leaves. As the genus name indicates, each stem has one flower. It flowers from early summer to early fall. First Nations people used it medicinally to rub on sores that would not heal. The fungal associates are limited to a small range of species, one being the false truffle Rhizopogon subcaerulescens.
Pinedrops is native to North America and has only one species, Pterospora andromedea. It grows in coniferous forests and is widespread across much of Canada, the United States, and Northern Mexico. When not flowering, they exist as a mass of fleshy roots. As with Monotropa, their fungal associates are limited to a few species of Rhizopogon. They do not associate with any other genus of fungus.
One of our common fall forest mushrooms is the short-stemmed Russula, Russula brevipes. Species of Russula are fungal associates of many mycoheterotrophic plants.
USDA Forest Service. What are mycotrophic wildflowers? https://www.fs.fed.us/wildflowers/beauty/mycotrophic/whatarethey.shtml
New Phytologist. The strange and wonderful mycoheterotrophs. http://parasiticplants.siu.edu/Mycotrophs/Mycotrophs.html