Reactions of Elm Wood to Attacks of Ophiostoma Ulmi (Buism.) Nannf.

Electron microscopy of elm infected with Ceratocystis ulmi (Buism) C Moreau

“…Tylose formation would thus be inhibited in the area of high hormonal concentration, the lesser concentration of adjacent vessels resulting in tylose stimulation. A similar relationship was formulated by Kerling (1955).…”

“…Yellowing extended to vessel walls and produced a continuous discoloration, as was also noted by Kerling (1955). The next visible change took place in the living protoplasm near affected vessels.…”

“…In other studies, tyloses were observed only in vessels in the proximity of other vessels containing fungal material (Kerling, 1955).…”

“…The occlusion of the conducting vessels of ulmi-infected elm by tyloses has been similarly observed (Schwarz, 1922;Wollenweber, 1929;Broekhuizen, 1929;Buisman, 1933;Clinton and McCormick, 1936;Kerling, 1955;Beckman, 1958;Ouellette, 1962;Wilson, 1965;Tchernoff, 1965). Schwarz (1922) stated that the first changes in appearance of infected elm wood were in the form of what she calls "bladder-like thylloses"…”

“…More recently, additional histological observations have added to knowledge about vascular discoloration (Kerling, 1955;Ouellette, 1962;Tchernoff, 1965;Wilson, 1965;Gagnon, 1967a,b), Kerling (1955) studied the changes in the diseased tissues of two European elm hybrids. She found that discoloration of the vessel and tracheal walls was the first visible alteration of elm tissue.…”