Abstract

MURACE, M. A.; SAPARRAT, M. C. N.; PERELLO, A.  and  LUNA, M. L.. Robinia pseudoacacia heartwood with evidence of rot: causal agent and anatomical and chemical characterization of the attacked wood. Quebracho (Santiago del Estero) [online]. 2022, vol.30, n.1, pp.18-30.  Epub Aug 01, 2022. ISSN 0328-0543.

Robinia pseudoacacia is recognized worldwide for its aesthetic importance and so cultivated in urban environments. The objective of this paper was to: identify the fungus responsible for the rot of Robinia pseudoacacia heartwood and analyze the anatomical and chemical alterations it causes in the wood. The samples were obained from trees growing in public spaces of La Plata City. The fungus identification was performed based on its cultural characteristics. Anatomical and chemical studies were performed in attacked and sound heartwood. For the LM observations the samples were fixed in FAA and embedded in Paraplast. The unstained sections were used to detect loss of birefringence (cellulolysis indicator). The MEB observations were made on samples mounted on stubs and covered with gold. For the chemical analysis FT-IR was used. The relationships between the absorbance levels corresponding to different chemical functional groups of the polymers of the attacked wood versus those obtained in control samples were estimated. The features of the pure cultures corresponded to L. sulphureus. The attacked wood presented brown discoloration, cubic pattern of fractures, abundant mycelium and chlamydospores. With LM and MEB it was observed: generalized tissue deformation; fractures; collapse of fibers; mycelium in vessels, rays and fractures; perforation in tyloses; eroded pits and complete loss of birefringence in fibers. Chemically, both the degradation of the carbohydrates over the lignin and the preferential attack of the guayacil units of the aromatic polymer were noticeable.

Keywords : black locust; heartwood; microstructural alterations; FT-IR; brown rot.