Ghostly Ericoid

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  Indian pipe flowersJohn Muir wrote: “When we try to pick out anything by itself, we find it hitched to everything else in the Universe.” This is certainly true of so much of what we see as horticulturists and plant lovers, from insects that induce plants to turn genes on and off and thus produce galls, to the cedar apple rust fungus that traverses its two-year life cycle in obligatory cycling between junipers and rosaceous plants.

From ants that tend aphids to lichens that are in mutualistic symbiosis between a fungus and an alga. From walnuts that produce juglone that discourages other plants from gaining rhizosphere space over walnut roots to the Entoloma fungus that infects the Armillaria fungus and thus changes its own form and edibility profile to humans.  

  One of the more amazing nature stories is the tripartite symbiotic relationship of Indian pipe or ghost plant (Monotropa uniflora) with mycorrhizal fungi such as Russula and roots of trees such as beech (Fagus). Monotropa uniflora was once considered parasitic on tree roots, one of thousands of parasitic plant species worldwide, partly because they must be parasitic on something since they do not produce chlorophyll, the pigment that helps most self-respecting plants harness energy from the sun via photosynthesis.

  It turns out, though, that Monotropa uniflora does not get food produced by trees directly, but rather from mycorrhizal fungi (“mycorrhiza” literally means “fungus-root”), that get their energy source from photosynthesizing trees. Indian pipe is actually parasitizing the fungus that is in a mutualistic symbiosis with the tree, since the mycorrhizal fungus that infects the tree roots helps the tree obtain minerals through extension of the fungal network into the soil, while the tree provides the energy source from carbohydrates via photosynthesis in leaves. This results in Indian pipe being termed a myco-heterotroph ("myco" for its connection to a fungus; "heterotroph" for the fact that Indian pipe does not produce its own food, which almost all plants do).  

  Wow. Indian pipe does produce chloroplasts, structures which typically contain chlorophyll, but somewhere along the evolutionary trail the production of chlorophyll and photosynthetic capacity was lost. It is almost enough to say that Monotropa is not a plant since it does not produce its own food, a key feature of planthood - but it does produce flowers, so is actually what would be considered a higher plant.

  For this species of Monotropa there is one flower per peduncle (flower stalk), thus the specific epithet of uniflora. These flowers, in terms of modern taxonomy place Monarda in the Ericaceae, the same family that includes rhododendron and azaleas, sourwood trees, pieris, and heathers. Flowers that were being visited by a bumblebee-like insect when I photographed these Indian pipes several days ago in the Shenandoah National Park (forgive the bee picture focus  – it was dark and hand-shaking spooky).  Truly, the variety and interrelationships of Nature are ever fascinating. As Glenn Keator wrote: “Nature seldom draws sharp boundaries around her creations.”

 

Indian pipe flower and pollinating bee