- Collection:
- Atlanta University and Clark Atlanta University Theses and Dissertations
- Title:
- Light and ultrastrucural observations on vascular dysfunction induced by ceratocystis ulmi in leaf and petiole traces of Ulmus Americana, 1976
- Creator:
- Hurd, Maggie P.
- Date of Original:
- 1976-07-01
- Subject:
- Degrees, Academic
Dissertations, Academic - Location:
- United States, Georgia, Fulton County, Atlanta, 33.749, -84.38798
- Medium:
- theses
dissertations - Type:
- Text
- Format:
- application/pdf
- Description:
- Light and ultrastructural observations on vascular dysfunction induced by Ceratocystis ulmi in leaf and petiole traces of Ulmus americana were conducted to determine the nature and extent of occurrence of vascular dysfunction at various stages of disease development in naturally infected twigs and in cuttings of American elm treated with sterile culture filtrates.Ultrastructural studies on anatomical changes in leaf and petiole traces of naturally infected and culture-filtrate treated elm twigs are lacking. It appears as if vascular dysfunction at these anatomical sites in elm may be critical in the water balance problem associated with wilting in Dutch elm disease. Observations at the levels of light and electron microscopy have revealed that vascular dysfunction is similar in leaf and petiole traces of naturally infected branches and in culture filtrate-treated cuttings. In both types of material vessel lumina were found to be occluded with granular or gum-like substances, vessel wall surfaces and middle lamellae were deteriorated, and intertracheary pit membranes were markedly darkened. In some instances, tylose-like bodies and bubble-like formations from the vessel wall occluded vessel lumina. Occasionally, hyphal segments were observed in vessel lumina in some traces from naturally infected twigs. Except for the presence of hyphal segments, vascular dysfunction in vessels in leaf and petiole traces from culture filtrate-treated cuttings, was indistinguishable from that in naturally infected material. The results of this study reveal the extent to which vascular dysfunction occurs in petiolar and leaf traces of elm infected by the Dutch elm disease fungus. Since these sites represent the only passageways for water to move to the leaf lamina extensive dysfunction in these areas should result in a critical water balance in the leaf blade. It appears likely, therefore, that leaf wilt in Dutch elm disease may be the direct result of vascular dysfunction at these anatomical sites.
Date of award: 7/1/1976
Degree type: dissertation
Degree name: Doctor of Philosophy (PhD)
Granting institution: Atlanta University
Advisor: Frederick, Lafayette - Metadata URL:
- http://hdl.handle.net/20.500.12322/cau.td:1976_hurd_maggie_p.pdf
- Holding Institution:
- Atlanta University Center Robert W. Woodruff Library
- Rights:
-
