A Beaded Endotrophic Mycorrhiza of Northern and Southern Red Oak

Abstract

An endotrophic mycorrhiza was found during a study of the morphological forms of ectotrophic mycorrhizae of northern red oak (Quercus rubra L.) and southern red oak (Q. falcata Michx.). The endotrophic type was frequently found on short roots of 7 northern red oaks and 4 southern red oaks from each of 3 locations in the Mountain, Piedmont, and Sand Hills regions of North Carolina. The mycorrhizae are beadlike (FIG. 1), with 1-9 beads in succession, dull white, and range from 2 to 8 mm in length and 0.4 to 0.8 mm in diam. Root hairs were not observed. Occasionally branched forms were found and in all instances, the branches were also beaded. To avoid mistaking roots for those of surrounding plants, all root samples were carefully traced back to the tree in question. Microscopically the type is a typical vesicular-arbuscular endotrophic mycorrhiza with intracellular hyphae (FIG. 2), well developed arbuscular haustoria (FIG. 3), and intracellular vesicles (FIG. 4). There was no evidence of a fungal mantle or Hartig net. Attempts to grow the fungal symbiont in pure culture failed. This endotrophic mycorrhiza is similar to those formed by species of Endogone (Gerdemann, personal communication). Most mycorrhizae formed by species of Quercus are ectotrophic (Trappe, 1962); however, Henry (1933), reported an ectendotrophic mycorrhiza on Q. rubra. To find an endotrophic mycorrhiza commonly occurring on red oak is unusual and to my knowledge, the form described has not been previously reported. Descriptions of beaded endotrophic mycorrhizae have been reported on roots of Acer platanoides L. (Henry, 1933), A. rubrum L. (McDougall, 1914; Henry, 1934; Vozzo and Hacskaylo, 1964), A. saccharum Marsh. (Kessler, 1966), Amelanchier canadensis (L.) Medic. (Henry, 1934), Cornus florida L. (Henry, 1933), Ilex opaca Ait. (Vozzo and Hacskaylo, 1964), Liquidambar styraciflua L. (Vozzo and Hacskaylo, 1964; Filer and Toole, 1966), and Nyssa sylvatica Marsh.; Populus alba L.; Prunus serotina Ehrh.; and Sorbus americana Marsh. (Henry, 1934). The beaded endotrophic mycorrhiza described in this report is simi408