Cross-field Pitting Characteristics of Reaction Wood in the Stem Wood of Pinus merkusii and Agathis loranthifolia

Abstract

This research investigated and compared the pitting type, pit number (PN), and pit diameter (PD) in the cross-field of compression wood (CWD), lateral wood (LWD), and opposite wood (OWD) in stem wood of Pinus merkusii and Agathis loranthifolia growing in Indonesia. Identification and quality evaluation were done using optical and scanning electron microscopy. A piceoid pit type was observed in the CWD of both species. The LWD and OWD of P. merkusii showed window-like and pinoid pits, whereas those of A. loranthifolia showed taxodioid and cupressoid pits. The PN and PD were the smallest in CWD of both species. In P. merkusii, LWD and OWD showed similar PN values, and PN in all parts increased from the pith to the bark. In A. loranthifolia, LWD had higher PN than in OWD, and PN in CWD and LWD decreased from near the pith to the bark, whereas in OWD, it increased. All parts of P. merkusii and CWD and OWD of A. loranthifolia showed a positive correlation between PN and radial tracheid diameter, whereas LWD showed a negative correlation. In P. merkusii, the PD of LWD approximated that of OWD, whereas, in A. loranthifolia, LWD had a larger PD than that exhibited by OWD.