Jennifer L. LaBundy
Project Topic / Abstract:
"An Ultrastructural Study of the Endophyte-Host Relationship of
Epichloč typhina and Elymus vrginicus"
A symbiotic relationship exists between the endophytic
fungus Epichloe‘ typhina and its host grass Elymus
virginicus. Infected grass individuals experience less
herbivory, due to fungally produced alkaloids, and tolerate
drought stress better than uninfected conspecifics.
Occasionally the fungus produces an epiphytic sexual phase,
known as a stroma, on the culm of some host tillers. Once
fertilized, a layer of perithecia forms over the "primary"
stroma. This study examined the ultrastructural aspects of
the Elymus-Epichloe’ system using light, scanning electron,
and transmission electron microscopy. First, the research
evaluated how the presence of the endophyte anatomically
affects its host, and tested the hypothesis that there are
structural differences (indicating possible physiological
differences) between leaves growing above the fungal stroma
and those growing below it. Several features were
morphologically compared, including gross leaf thickness,
cuticle thickness, epidermal cell wall thickness, stomatal
density, bulliform cell size, and chloroplast ultrastructure.
Secondly, the epiphytic fungal phase was critically
examined. Each perithecium, resembling a flask-shaped
chamber, has a two-zoned wall, an opercular cap delimited by
a distinct histological layer, and contains filiform asci.
This study is the first to morphologically investigate the
Elymus-Epichloe‘ symbiosis, and is the first to document the ultrastructural nature of the "primary" and perithecial
stromal stages for any stroma-bearing endophyte.
National Conference of Undergraduate Research (Schenectady,
1995 Truman Undergraduate Research
Symposium (Kirksville, MO)
1995 Sigma Xi Research Symposium