Author

Richard Wynia

Document Type

Thesis - Open Access

Award Date

1985

Degree Name

Master of Science (MS)

Department

Plant Science

Abstract

American licorice is a herbaceous, perennial, native legume common to disturbed areas, draws, woods, and depressions in prairies and pastures over much of temperate North America. It is utilized by livestock in the Great Plains and produces nutritious and highly digestible forage. However, forage value or use reports for this species have been inconsistent. Reports ranged from "relished by livestock" to "withstands excessive use" depending on location of utilization and author cited. Glycyrrhiza contains tannic acid and palatability of some forage legumes has been influenced by their tannic acid content. Severe natural infections of rust were noted in a licorice ecotype nursery in June 1984 at Brookings, South Dakota. Severe infections normally induce leaf loss and create a subsequent reduction in forage quality. Our objectives in undertaking this ultrastructural examination of G. lepidots and its associated rust pathogen U. glycyrrhizae were to study the fine structure of the host-pathogen interaction and to examine the pathogen and its legume host for unique cell types, cellular organelles, and other cellular inclusions, such as tannin. Rust-infected leaves were collected in June, fixed in glutaraldehyde and osmic acid, dehydrated, and then embedded in epoxy plastic. Polymerized epoxy blocks were sectioned with an ultramicrotome. Sections were mounted on copper grids, stained with uranyl acetate and lead citrate, and subsequently viewed with the transmission electron microscope. Electron micrographs of rust hyphae in intercellular spaces of host vascular parenchyma and mesophyll cells elucidated the development of U. glycyrrhizae. The typical dikaryotic nuclear condition and fungal organelles were observed in intercellular hypha. Intercellular hyphae formed haustorial mother cells that penetrated host cell walls and formed dikaryotic intracellular haustoria. Haustoria were surrounded by extrahaustorial sheaths which delimited intimate contact of haustoria to host cytoplasm. Micrographs of intact host mesophyll cells showed lens-shaped chloroplasts with short grana stacks, nuclei, nucleoli, mitochondria, and microbodies. Vascular parenchyma cells contained numerous small vacuoles, mitochondria, dictyosomes, chloroplasts, and invaginations of cellular plasmalemmas. Two types of specialized parenchyma cells were also observed for the first time in Glycyrrhiza. A-type transfer cells, which specialize in short distance solute transport, were located in minor leaf veins. Tannin cells, which package and store tannins, were found in leaf mesophyll cells.

Library of Congress Subject Headings

Licorice (Plant) -- Diseases and pests
Rust fungi

Format

application/pdf

Number of Pages

80

Publisher

South Dakota State University

Rights

No Copyright - United State
http://rightsstatements.org/vocab/NoC-US/1.0/

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