Abstract Detail

Paleobotany

Harper, Carla J [1], Taylor, Thomas N [2], Krings, Michael [3].

Life after arbuscules: Interfungal interactions from the Devonian Rhynie chert.

Arbuscular mycorrhizas are among the most important symbioses on Earth. The physiological interface occurs in the form of special structures termed arbuscules, which are formed by the fungus in selected cells of the host plant. However, arbuscules are ephemeral structures that collapse after only a few days. This is in contrast to other parts of the mycorrhizal fungus (e.g., trunk hyphae, vesicles), which appear to remain intact for some time after arbuscule senescence. Few studies have addressed the fate of vesicles and trunk hyphae in roots without active arbuscules. The Early Devonian Rhynie chert has yielded multiple specimens of mycorrhizal land plant axes displaying post-arbuscule states of the mycorrhizal fungus. These specimens indicate that trunk hyphae may become segmented, with the individual segments perhaps functioning as propagules. On the other hand, vesicles regularly act as hosts for a diverse suite of microfungi, which may occur as mycelia, spores of varying diameters, and amorphous residue. Based on structural features and developmental sequences gathered from >500 specimens, the vesicle-colonizing microfungi in the Rhynie chert fall into three major groups: (1) clusters of spheroidal spores (8–50 μm diam) developing in pairs from short hyphal branches, which are given off from a central hypha; (2) clusters of spheroidal spores (5–25 μm diam) developing simultaneously with a mycelium; (3) membrane-bounded, sac-like structure within which occur dark amorphous matter and one to several thin-walled spores ~10 µm diam. The spores appear to form as a result of the partitioning of the amorphous matter. The abundance of microfungi in glomeromycotan vesicles in the Rhynie chert suggests that the vesicles in some way positively affected sporulation or spore development in these microfungi, perhaps as a result of confined space and certain nutrients, or that the vesicles provided protection from some degradative agent. The systematic assessment of the microfungi colonizing glomeromycotan vesicles in the Rhynie chert contributes to our understanding of the multiple levels of organismal interactions that sustained early non-marine ecosystems.

1 - Ludwig-Maximilians-Universität, Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, and SNSB-Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Straße 10, Munich, 80333, Germany
2 - University Of Kansas, Department Of Ecology And Evolutionary Biology, 1200 Sunnyside Avenue, Haworth Hall, Lawrence, KS, 66045-7600, USA
3 - Ludwig-Maximilians-Universität, Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, and SNSB-Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Straße 10, Munich, 80333, Germany

Keywords:
fossil funngi
Symbiosis
mycorrhiza
interaction
Paleozoic
root.

Presentation Type: Oral Paper
Session: 23, Paleozoic and Mesozoic Paleobotany
Location: 102/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 8:30 AM
Number: 23002
Abstract ID:186
Candidate for Awards:None