Interspecies Interactions

The most notable interaction H. peckii has with other organisms is the ectomycorrhizae if forms with trees, almost always conifers. Specfically,  H. peckii is known to form ectomycorrhizae with the genera Pinus (pines), Picea (spruces),  Tsuga (Hemlock), Peeudotsuga (Douglas Fir), and possibly Betula (birches) (Newton et al.). Ectomycorrhizae are symbiotic associations between fungi and plants in which the roots of the host plant are enveloped in a  'sheath' of fungal hyphae.  As the plant root grows, the hyphae encasing the root grow with it. Additionally, the hyphae from the fungus excrete enzymes called pectinases which allow the hyphae to nestle themselves in between the outer cells of the plant root and form what is referred to as a Hartig net. The vast surface area of the Hartig net serves as the primary junction of chemical exchange between H.peckii and its symbiont (Moore et al., 2011). The figure above shows a cross-section of an ectomycorrhiza. The sheath of hyphae encapsulating the plant root has been labeled (a),  a plant root cell has been labeled (b), and (c) denotes the Hartig net.

The ectomycorrhizae H. peckii contributes to are mutualistic—both fungus and plant benefit.  H. peckii shares water and nutrients such phosphorus, potassium, and nitrogen with with plant, while the plant reciprocates by sharing carbohydrates. The ectomycorrhizal relationship between  H.peckii and conifers has been so engrained by evolution that neither species can survive without the other.  H.peckii is dependent upon carbohydrates from  the conifer because it is no longer versed in sapotrophy (decomposing) like most other fungi.  Likewise, the conifer relies on H.peckii, or other ectomycorrhizal fungi, because these fungi secrete enzymes and acid that give trees access to many organic nutrients that would be otherwise unavailable to them. The inset labeled (a) in the diagram to the right illustrates enzyme-facilitated nutrient acquisition by the fungus in which the fungus secretes an enzyme that liberates organic nutrients such as phosphorus and nitrogen from the soil and absorbs them to share with the plant. The inset labeled (b) shows how the fungi use acid to help break down rocky substrates and access their nutrients.  Not only do ectomycorrhizal fungi contribute precious nutrients to their relationships, they also provide extensive surface area with their mycelia to augment the sheer nutrient uptake capacity (Landeweert et al. 2001).

It is also notable that trees in association with ectomycorrhizal fungi have suppressed root hair development, which hinders their ability to absorb nutrients without aid (Moore et al., 2011).  Such a relationship in which both parties need the other to survive is termed an obligate mutualism. The uniquely intimate relationship between H.peckii and its arboreal symbionts can be exploited by 'seeding' trees with H.peckii to aid reforestation efforts.

Ectomycorrhizae are more than just a relationship between a fungus and tree, they also connect trees with other trees by creating a 'wood-wide-web' (Moore et al. 2011). This expansive underground latticework of mycelia and roots enables intercellular communication between many organisms and facilitates their aggregate ability to adapt to changing environmental conditions.

Ectomycorrhizae aside, you may be wondering what other types of interactions H. peckii has. The answer may be dissatisfying. Due to its acrid, aversive taste (and despite its tantalizing resemblance to a scrumptious French pastry) you won't encounter many sylvan critters munching on H. peckii. The closest thing to predation H. peckii encounters is in its interactions with the dreaded Homo sapiens. Although H.peckii is non-toxic, it is too bitter for human palatability;however, humans sometimes pick H.peckii to use in mushroom dying. Also, human contributions of atmospheric nitrogen pollution may have an adverse affect on H. peckii which is known to be especially sensitive to nitrogen deposition in the soil (Van der Linde et al. 2009).  In summary: H. peckii is kind of an introvert, its best friends are conifers, and humans are conceited bullies.

Now, hang on to your hyphae—it's time for a spooky story.