The shape of soft-rot cavities—A hypothesis

Abstract

It has been known for a long time that a group of lower fungi now called soft-rot fungi, chiefly members of the Ascomycetes and Fungi Imperfecti, produce a decay pattern in the $2 layer of wood cell walls consisting of cavities which in surface view of the wall are diamond shaped with smooth sides and pointed corners or have parallel sides with pointed ends. These may occur singly or in chains and the longer axis of the cavity and of the chains lies in the direction of the preferred orientation of the cellulose microfibrils constituting the $2 layer. The cavities were first described by Schacht and the developments in the literature since then have been reviewed by Levy (1965) and Findlay (1970). The mode of attack on the walls by soft-rot fungi is now well established (Corbett, 1963; 1965; Corbett, Levy, 1963; Greaves, Levy, 1965; Levy, Stevens, 1966). A hypha lying in the lumen sends out laterally a fine hypha which bores through the $3 layer into the $2 layer where it forms a T-branch. The arms of the branch grow through the wall in each direction parallel to the microfibrils of the wall as broader hyphae which then form the cavities. It is the purpose of this paper to present a testable, semi-quantitative hypothesis to explain the shape of these cavities in terms of the known architecture of the $2 layer of the wood cell wall. Hardwoods are known to be more susceptible to soft-rot attack than are softwoods, though softwoods do yield cavities (Savory, 1954), and this is commonly attributed to the lower lignin content of the walls of hardwoods. Non-wood fibres -even cotton hairs, which do not contain lignin-are also attacked by soft-rot organisms with cavity formation (Nilsson, 1974) though no cavities are produced with delignified wood or with rubbery wood (in which lignin synthesis is disturbed) (Findlay, 1970). The relation between lignin content and cavity formation is therefore complex. It is known, however, that the enzymes excreted to the substrate by,

DOI: 10.1007/BF00350220

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@article{Preston2004TheSO, title={The shape of soft-rot cavities—A hypothesis}, author={Rhonda D Preston}, journal={Wood Science and Technology}, year={2004}, volume={13}, pages={155-163} }