Mycorrhizal Mushrooms: Fungus and Plant Partnerships

Mycorrhizal Mushrooms: Fungus and Plant Partnerships 




Mycorrhizal mushrooms (myco means “mushroom”; rhizal means “related to roots”), such as matsutake, boletus, and chanterelles, form mutually beneficial relationships with pines and other plants. In fact, most plants from grasses to Douglas firs have mycorrhizal partners. The mycelia of fungal species that form exterior sheaths around the roots of partner plants are termed ectomycorrhizal. The mycorrhizal fungi that invade the interior root cells of host plants are labeled endomycorrhizal, although currently the preferred term for these fungi is vesicular arbuscular mycorrhizae (VAM).
Both plant and mycorrhizae benefit from this association. Because ectomycorrhizal mycelium grows beyond the plant’s roots, it brings distant nutrients and moisture to the host plant, extending the absorption zone well beyond the root structure. The mycelium dramatically increases the plant’s ingestion of nutrients, nitrogenous compounds, and essential elements (phosphorus, copper, and zinc) as it decomposes surrounding debris. David Perry (1994) postulates that the surface area—hence its absorption capability—of mycorrhizal fungi may be 10 to 100 times greater than the surface area of leaves in a forest. As a result, the growth of plant partners is accelerated. Plants with mycorrhizal fungal partners can also resist diseases far better than those without. Fungi benefit from the relationship because it gives them access to plant-secreted sugars, mostly hexoses that the fungi convert to mannitols, arabitols, and erythritols. 
One of the most exciting discoveries in the field of mycology is that the mycorrhizae can transport nutrients to trees of different species. One mushroom species can connect many acres of a forest in a continuous network of cells. In one experiment, researchers compared the flow of nutrients via the mycelium between 3 trees: a Douglas fir (Pseudotsuga menziesii), a paper birch (Betula papyrifera), and a western red cedar (Thuja plicata). The Douglas fir and paper birch shared the same ectomycorrhiza, while the cedar had an endomycorrhiza (VAM). The researchers covered the Douglas fir to simulate deep shade, thus lowering the tree’s ability to photosynthesize sugars. In response, the mycorrhizae channeled sugars, tracked by radioactive carbon, from the root zone of the birch to the root zone of the fir. 
More than 9 percent of the net carbon compounds transferred to the fir originated from the birch’s roots, while the cedar received only a small fraction. The amount of sugar transferred was directly proportional to the amount of shading (Simard et al. 1997). An earlier study by Kristina Arnebrant and others (1993) showed a similar bidirectional transfer of nitrogen-based nutrients from alder (Alnus glutinosa) to pine (Pinus contorta) through a shared ectomycorrhizal mycelium.

Commentaires

Enregistrer un commentaire

Posts les plus consultés de ce blog

The Mycelial Archetype

Image
The Mycelial Archetype  Nature tends to build upon its successes. The mycelial archetype can be seen throughout the universe: in the patterns of hurricanes, dark matter, and the Internet. The similarity in form to mycelium may not be merely a coincidence. Biological systems are influenced by the laws of physics, and it may be that mycelium exploits the natural momentum of matter, just like salmon take advantage of the tides. The architecture of mycelium resembles patterns predicted in string theory, and astrophysicists theorize that the most energy-conserving forms in the universe will be organized as threads of matterenergy. The arrangement of these strings resembles the architecture of mycelium. When the Internet was designed, its weblike structure maximized the pooling of data and computational power while minimizing critical points upon which the system is dependent. I believe that the structure of the Internet is simply an archetypal form, the inevitable consequence o...
Lire la suite

The Medicinal Mushroom Forest

Image
The Medicinal Mushroom Forest Forest dwellers long ago discovered the value of medicinal mushrooms for the healing  of both the body and the forest. Sadly, most of our ancestors’ empirical knowledge is  lost, but what little survives hints at a rich, albeit vulnerable, resource.  The science of  soils—mapping the matrix of plant, animal, and microbial communities in a habitat  remains in its infancy. Researchers have shown, however, that the forest is thoroughly  interlaced with fungal nets of mycorrhizal, saprophytic, parasitic, and endophytic  species. Mushrooms are forest guardians. A forest ecosystem cannot be defined  without its fungi because they govern the transition between life and death and the  building of soils, all the while fueling numerous life cycles. Primary saprophytes initiate  the decomposition process, and what the saprophytes don’t break down, the  mycorrhizal fungi do. I suspect that the overlying s...
Lire la suite