Developmental and Structural Section
Erwin, , Hwang, Won-Joung , Takemoto, S , Itoh, Takao , Imamura, Yuji .
Decay features of xylem on the cankerous tree of tropical wood species.
A serious stem canker of tropical wood species has been found in East Kalimantan, Indonesia. The species are rubber tree (Hevea brasiliensis Muell. Arg.) in a rubber plantation replanting area and light red meranti tree (Shorea smithiana Sym.) in a natural tropical rain forest. Fungal infection of standing trees is suspected as a main causal factor of disease and xylem decay. Colonization of fungal hyphae on xylem tissues was clearly observed under light microscopy and scanning electron microscopy. Xylem fibers, rays and parenchymal cells of both cankers were degraded, but most vessel elements remained intact. Penetration by the fungal hyphae into xylem cells caused numerous holes in fiber and axial parenchymal cell walls, and pits in vessel elements became distorted and enlarged. Tylose formation was commonly observed in vessels. Although the tyloses were considered to impede both fungal invasion and localization of infection, this study found that the fungi could penetrate the tyloses. On S. smithiana, separation of the cells was common, but xylem cells adjacent to the resin canal were not separated. The loss of small numbers of axial parenchymal cell walls and the thinning of fiber walls were also detected. On H. brasiliensis, separation of the cells due to the partial degradation of middle lamella was observed mainly in fibers. Many of them showed concentric degradation of cell walls starting from the lumen surface.
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1 - Research Institute for Sustainable Humanosphere (RISH), Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
2 - Graduate School of Agriculture, Kyoto University, Sakyo-Ku, Kyoto, 606-8502, Japan
Tropical wood species.
Presentation Type: Oral Paper:Papers for Sections
Location: 312/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 9:15 AM