ANATOMICAL CHARACTERISATION OF TEAK (TECTONA GRANDIS) WOOD DECAYED BY FUNGUS CHRYSOSPORIUM ASPERATUM

Teak wood logs are most often invaded by Chrysosporium asperatum. The extent of damage caused by it within a given period was investigated by in-vitro decay test. Sound wood blocks of Tectona grandis inoculated with C. asperatum showed no appreciable weight loss in the early phase of fungal colonisation but registered a 34—38% weight loss within three months. At the outset, fungal mycelia entered into wood tissue through vessels and xylem rays, invading all cell types by ramifying through pits on lateral walls. Fungal invasion commenced from the cell corners and the middle lamellae of the fibre wall, without any pronounced effect on the primary and secondary wall layers. Xylem cells were separated due to dissolution of middle lamella in the early stage, but in the advanced stages of decay all cell types showed formation of erosion channels and bore holes. In the advanced stage of infection, vessels were deformed due to explicit degeneration and eventually collapsed due to loss of rigidity. Xylem rays were more vulnerable to degradation than axial elements. Structural alterations induced in response to fungal invasion are described in the paper. Balak pokok jati sering diserang oleh Chrysosporium asperatum. Tahap kerosakan akibatnya dalam tempoh tertentu disiasat secara ujian pereputan in-vitro. Blok kayu Tectona grandis yang berkeadaan baik diinokulasi dengan C. asperatum tidak menunjukkan sebarang kehilangan berat yang ketara pada awal fasa pengkolonian kulat. Namun, setelah tiga bulan, kehilangan berat sebanyak 34% hingga 38% diperhatikan. Pada permulaanya, miselium memasuki tisu kayu melalui salur vesel serta salur xilem lalu menyerang semua jenis sel secara bercabang-cabang melalui lubang-lubang halus pada dinding lateral. Serangan kulat bermula dari sudut sel hingga ke lamela tengah dinding gentian tanpa memberi kesan kepada lapisan dinding primer serta sekunder. Sel xilem terasing akibat penguraian lamela tengah pada peringkat awal. Namun, pada peringkat pereputan yang lebih lewat, semua jenis sel menunjukkan pembentukan alur hakisan dan lubang penebukan. Pada peringkat ini, vesel berubah bentuk akibat kemerosotan yang nyata dan akhirnya runtuh kerana kehilangan ketegaran. Salur xilem lebih terkesan terhadap kemerosotan berbanding dengan unsur aksial. Perubahan struktur akibat tindak balas serangan kulat dihuraikan dalam kertas kerja ini.