516 Characterization of red alder ectomycorrhizae: a preface to monitoring belowground ecological responses
STEVEN L. M ILLER AND C. D. Koo Department of Forest Science, Oregon State University, Corvallis, OR 97331, U.S.A.
AND
R ANDY MOLINA United States Department of Agriculture, Forest Service, Pacific Northwest Research Station, Forestry Sciences Laboratory, 3200 Jefferson Way, Corvallis, OR 97331, U.S.A. Received May 2, 1990
M ILLER, S. L., Koo, C. D., and M OLINA, R. 1991. Characterization of red alder ectomycorrhizae: a preface to monitoring belowground ecological responses. Can. J. Bot. 69: 516-531. Critical ecological research on belowground ecosystems has often been impeded because of the inability to adequately recognize ectomycorrhizal relationships, especially the abundance, diversity, and distribution of the fungus component, and the specificity of particular fungus—host combinations. Red alder, with its high degree of host specificity and paucity of fungal symbionts, provides an ideal model for studying these attributes. Eleven morphologically recognizable types of ecto- mycorrhizae were characterized from field-collected root material, greenhouse soil bioassays, and laboratory syntheses. Most mycobionts were basidiomycetes, as evidenced by abundant clamp connections present in the mantle and extramatrical hyphae. Seven mycobionts identified to species included Alpova diplophloeus, Thelephora terrestris, Lactarius obscuratus, Cortinarius bibulus, Laccaria laccata, Hebeloma crustuliniforme, and Paxillus involutus. Many of the ectomycorrhizae collected in the field appeared to have more than one mycobiont present in the mantle. Root tips could generally be categorized into either flexuous or succulent morphological types. The flexuous types were long, thin, indeterminate in growth, with an acute root apex, and the mantle and Hartig net in longitudinal section were not well formed near the root apex. The succulent types were short, thick, determinate in growth, with a rounded root apex, and the mantle and Hartig net in longitudinal section were well formed near the root apex. Additional characteristics important in distinguishing among red alder ecto- mycorrhizal types included color, extent of extramatrical hyphae development, mantle surface characteristics, and selected microchemical reactions. Mantle thickness was highly variable and not useful in characterization. Hartig net development was shallow, and regardless of mycorrhizal origin, rarely extended beyond one epidermal cell layer. Key words: ectomycorrhizae, Alnus, characterization, ecology, belowground.
M ILLER, S. L., Koo, C. D., et MOLINA, R. 1991. Characterization of red alder ectomycorrhizae: a preface to monitoring belowground ecological responses. Can. J. Bot. 69 : 516-531. La recherche ecologique critique sur les ecosystemes souterrains a souvent ete limit par l incapacite a reconnaitre de fawn valable les relations ectomycorhiziennes, en particulier, l abondance, la diversite et la distribution de la composante fongique ainsi que la specificite des combinaisons hOtes—champignons particulieres. L aulne rouge, avec une forte specificite de l hOte et une pauvrete en espêces fongiques, constitue un modele ideal pour ( etude de ces proprietes. A partir de materiel racinaire recolte aux champs, d essais en serre et de syntheses au laboratoire, les auteurs ont caracterisd 11 types d ecto- mycorhizes reconnaissables morphologiquement. La plupart des mycobiontes sont des basidiomycetes, tel que demontre par la presence d abondantes boucles d anastomose dans les hyphes des manchons et du mycelium extrammatriciel. On reconnait sept espêces de mycobiontes incluant Alpova diplophloeus, Thelephora terrestris, Lactarius obscuratus, Cortinarius bibulus, Laccaria laccata, Hebeloma crustiliniforme et Paxillus involutus. Plusieurs des mycorhizes recoltees sur le terrain semblent contenir plus d une espece de champignon symbiotique dans leur manchon. Les extremites racinaires peuvent habituellement être attribuees aux types morphologiques flexueux ou succulents. Les mycorhizes de types flexueux sont longues, minces, de croissance indeterminee, pourvues d un apex pointu et montrent en section longitudinale un manchon et un reseau de Hartig pas tres bien formes pres de l apex. Les mycorhizes de types succulents sont courtes, epaisses, de croissance deter- minee, pourvues d un apex racinaire arrondi et montrent en section longitudinale un manchon et un reseau de Hartig bien developpes jusqu au voisinage de l apex racinaire. Parmi les autres caracteristiques importantes permettant de distinguer les types ectomycorhiziens de l aulne, on retrouve la couleur, l étendue du developpement de la phase extramatricielle, les caracteres superficiels du manchon et des reactions microchimiques selectionnees. L epaisseur du manchon varie fortement et ne constitue pas un caractere tres utile. Les developpement du reaseau de Hartig est peu profond et, quel que soft l origine mycorhizienne, ne s etend que rarement au dela d une couche de cellule ápidermique. Mots des : ectomycorhizes, Alnus, caracterisation, ecologie, souterrain. [Traduit par la redaction]
Introduction research has begun to emphasize the ecological importance of ectomycorrhizae and the mycobionts in belowground eco- Ectomycorrhizae are well known for improving survival and system processes and plant community dynamics. However, growth of forest trees. Consequently, much research has con- our inability to adequately identify or recognize mycobionts centrated on practical applications in forestry. Recently, and their ectomycorrhizae continues to hamper efforts to understand the individual contributions of diverse symbionts Present address: Botany Department. University of Wyoming. Laramie, WY 82071, U.S.A. in these ecological processes.
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