Pterospora

Pterospora, commonly known as pinedrops,[1] woodland pinedrops,[2] Albany beechdrops, or giant bird's nest is a North American genus in the subfamily Monotropoideae of the heath family, and includes only the species Pterospora andromedea.[3][4] It grows as a mycoheterotroph (relying on fungi rather than photosynthesis for nutrients) in coniferous or mixed forests. It is widespread across much of Canada as well as the western and northeastern United States to northern Mexico (Sonora, Coahuila, Durango, Nuevo León and Baja California).[5][6] Along with Monotropa it is one of the more frequently encountered genera of the Monotropoideae.[7][8]

The fruits are five-celled woody capsules (Wenatchee Mountains, Washington).

Pterospora
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Ericales
Family: Ericaceae
Subfamily: Monotropoideae
Tribe: Pterosporeae
Genus: Pterospora
Nutt. 1818
Species:
P. andromedea
Binomial name
Pterospora andromedea
Nutt. 1818

The genus name is derived from the morphology of the seeds which have narrow flaps of tissue on the side and therefore appear winged: pteron (Gr.) = wing, spora (Gr.) = seed. The specific name andromedea derives from the resemblance of the flowers to those of another genus in the Ericaceae, Andromeda.[7][8]

The visible portion of Pterospora andromedea is a fleshy, unbranched, reddish to yellowish flower spike (raceme) 30–100 cm (12–39.5 in) in height, though it has been reported to occasionally attain a height of 2 meters (6.6 feet). The above-ground stalks (inflorescences) are usually found in small clusters between June and August. The inflorescences are hairy and noticeably sticky to the touch. This is caused by the presence of hairs which exude a sticky substance (glandular hairs). The inflorescences are covered by scale-like structures known as bracts. The upper portion of the inflorescence has a series of yellowish, urn-shaped flowers that face downward. The fruit is a capsule.[8] Plants exist for most of their life as a mass of brittle, but fleshy, roots.

Pterospora has consistently been shown to be more closely related to Sarcodes than any other member of the Monotropoideae.[9]

Fungal Interactions

P. andromedea, like all members of Monotropoideae, is a mycoheterotroph. This is a form of carbon acquisition that is parasitic on fungal organisms and epiparastic of photosynthetic plants which are symbionts to the fungal host. Because P. andromedea is achlorophyllous[10] this relationship is an obligate symbiosis for it, but is not ubiquitous in the fungal host. All monotropoideae are host specific to a select few fungal counterparts which in turn makes them specific to the photosynthetic organism associated with their fungal host. In the case of P. andromedea fungal host specificity leans heavily towards Rhizopogon salebrosus[11] in the western distribution and Rhizopogon kretzerae[12][13] in the eastern distribution but broadly seems to be ubiquitous symbionts with Rhizopogon subgenus Amylopogon.[8][9][14] Rhizopogon species also exhibit high host specificity and sub-genus Amylopogon is primarily associated with the Pinus genus. Fungal exoenzymatic activity has been shown to be required for seed germination of P. andromedea however the requisite enzymes are not exclusively produced within subgenus Amylopogon indicating that seed colonization by fungi outside of the observed host specificity is possible however ecologically restricted by some currently unknown mechanism.[15]

See also

References
  1. USDA, NRCS (n.d.). "Pterospora". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 15 October 2015.
  2. USDA, NRCS (n.d.). "Pterospora andromedea". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 15 October 2015.
  3. "United States Department of Agriculture plants profile: Pterospora andromedea Nutt". Retrieved 2008-08-15.
  4. Biota of North America Program 2014 county distribution map
  5. SEINet, Southwestern Biodiversity, Arizona chapter
  6. Rebman, J. P.; Gibson, J.; Rich, K. (2016). "Annotated checklist of the vascular plants of Baja California, Mexico" (PDF). San Diego Society of Natural History. 45: 139.
  7. Wallace, G.D. (1975), Studies of the Monotropoidiae (Ericaceae): taxonomy and distribution, The Wassman Journal of Biology
  8. Flora of North America, Pterospora Nuttall, 1818.
  9. Bidartondo, M.I.; Bruns, T.D. (2001), "Extreme specificity in epiparasitic Monotropoideae (Ericaceae): widespread phylogenetic and geographical structure", Molecular Ecology, 10 (9): 2285–95, doi:10.1046/j.1365-294x.2001.01358.x, PMID 11555270
  10. Cummings, Michael P.; Welschmeyer, Nicholas A. (1998), Pigment composition of putatively achlorophyllous angiosperms, Plant Systematics and Evolution
  11. Dowie, Nicholas J.; Grubisha, Lisa C.; Burton, Brent A.; Klooster, Matthew R.; Miller, Steven L. (2017-01-02). "Increased phylogenetic resolution within the ecologically important Rhizopogon subgenus Amylopogon using 10 anonymous nuclear loci". Mycologia. 109 (1): 35–45. doi:10.1080/00275514.2017.1285165. ISSN 0027-5514. PMID 28402794. S2CID 12476105.
  12. Grubisha, Lisa C.; Dowie, Nicholas J.; Miller, Steven L.; Hazard, Christina; Trowbridge, Steven M.; Horton, Thomas R.; Klooster, Matthew R. (July 2014). "Rhizopogon kretzerae sp. nov.: the rare fungal symbiont in the tripartite system with Pterospora andromedea and Pinus strobus". Botany. 92 (7): 527–534. doi:10.1139/cjb-2013-0309. ISSN 1916-2790.
  13. Hazard, Christina; Lilleskov, Erik A.; Horton, Thomas R. (2011-10-12). "Is rarity of pinedrops (Pterospora andromedea) in eastern North America linked to rarity of its unique fungal symbiont?". Mycorrhiza. 22 (5): 393–402. doi:10.1007/s00572-011-0414-y. ISSN 0940-6360. PMID 21989709. S2CID 3259872.
  14. KW Cullings, TM Szaro, TD Bruns. 1996. "Evolution of extreme specialization within a lineage of ectomycorrhizal epiparasites" - Nature 379:63-65
  15. BRUNS, THOMAS D.; READ, DAVID J. (2000-11-27). "In vitro germination of nonphotosynthetic, myco-heterotrophic plants stimulated by fungi isolated from the adult plants". New Phytologist. 148 (2): 335–342. doi:10.1046/j.1469-8137.2000.00766.x. ISSN 0028-646X.
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