The Delignification Pattern of Ailanthus excelsa Wood by Inonotus hispidus (Bull.: Fr.) P. Karst.

Abstract

In vitro laboratory decay tests on Ailanthus excelsa Roxb. wood revealed that I. hispidus exhibits a combination of both white-rot and soft-rot patterns of wood decay. Early stages of wood decay showed dissolution of the middle lamella as well as defibration and localized delignification of fiber walls; vessels, axial, and ray parenchyma remained unaltered. Delignification commenced from the middle lamellae at the cell corners without any marked effect on the primary and secondary wall layers. In later stages of growth, the species produces typical soft-rot decay pattern by forming erosion channels through the S2 layers of fiber walls, transverse bore holes in the cell walls, and erosion channels alongside/following the orientation of cellulose microfibrils. The rays showed signs of cell wall alterations only after the extensive damage to the fiber walls. After 120 days of incubation, the vessels also showed localized delignification, the erosion of pits, and separation from associated xylem elements. The extensive weight losses under natural and in vitro decayed wood as well as the very soft nature of severely degraded wood indicate that I. hispidus alters wood strength and stiffness.