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Cytology and Histology

Hyphal Morphology of Botryosphaeria dothidea in Vessels of Unstressed and Drought-Stressed Stems of Betula alba. J. M. McPartland, Research assistant, Department of Plant Pathology, University of Illinois, and Illinois Natural History Survey, 172 Natural Resources Building, 607 East Peabody, Champaign 61820; D. F. Schoeneweiss, professor, Department of Plant Pathology, University of Illinois, and Illinois Natural History Survey, 172 Natural Resources Building, 607 East Peabody, Champaign 61820. Phytopathology 74:358-362. Accepted for publication 1 November 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-358.

Hyphae in unstressed stems of white birch seedlings were thin, contorted, highly vacuolated, and restricted to xylem vessels within 5 mm of inoculation wounds. Hyphae in drought-stressed stems were thick, branched, rectilinear, and spread extensively through vessels. SEM photographs revealed a two-layered sheath on all hyphae appressed to vessel walls in stressed stems, but the sheath was seen only rarely in unstressed stems. A significantly greater number of hyphal apices in unstressed stems were either swollen or had burst and released amorphous cytoplasm. Removal of cytoplasm with H₂O₂ + KOH revealed distinct holes in hyphal walls at bursted apices. A microfibrillar mesh was observed occasionally in vessels of inoculated unstressed stems.