Hardness and fracture morphology of reaction wood from Pinus merkusii and Agathis loranthifolia

초록

This study aimed to evaluate and compare the fracture morphology in hardness test of compression (CW), lateral (LW), and opposite woods (OW) of Pinus merkusii and Agathis loranthifolia growing in Indonesia. The hardness of the transverse, radial, and tangential surfaces was examined using Brinell's method, according to the Korean standard. The fracture surfaces of hardness tested samples were observed by scanning electron and optical microscopy. On all surfaces from both species, CW showed the highest hardness, and no significant differences were detected between LW and OW. On the transverse surface, CW of P. merkusii showed brittle-fractured cell wall, while that of A. loranthifolia displayed smooth cell wall. CW of both species showed intercellular and intrawall failures and a narrow lumen opening. LW of both species and OW of P. merkusii showed folded earlywood tracheids with a crack, whereas in the latewood of P. merkusii, LW and OW displayed smooth cell wall and a narrow lumen opening. OW of A. loranthifolia showed collapsed cell wall. On the radial surface, CW of both species showed buckling tracheids in the tangential direction. LW and OW of both species exhibited shortening earlywood tracheids with folded cell walls, while LW and OW of P. merkusii exhibited buckling latewood tracheids in the radial direction. On the tangential surface, buckling tracheids occurred near the fractured rays in all parts of both species. In conclusion, CW exhibited distinctive hardness and fracture morphologies compared with LW and OW in P. merkusii and A. loranthifolia; in addition, hardness and fracture morphology differed between the two species.

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