ANATOMICAL CHARACTERIZATION OF REACTION WOOD IN ANGSANA (PTEROCARPUS INDICUS WILLD.)

• Main Author: Junita, Irma
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/85841
• Institution: Institut Teknologi Bandung

The formation of reaction wood is a structural adaptation in the growth of wood that experiences mechanical stress in tilted stems or branches to prevent damage. In angiosperms, reaction wood forms on the upper side of the tilted stem to pull the stem upward and prevent it from breaking, while the opposite side that experiences mechanical stress is known as opposite wood. This study aims to evaluate the anatomical characteristics of reaction and opposite wood in Pterocarpus indicus Willd. through the observation of sections on radial, tangential, and transverse planes, as well as measurements of fiber and trachea dimensions. The wood used in this research was sourced from the ITB Jatinangor campus. Samples consisted of wood slabs taken from the main stem at a height of 1.3 meters above ground level. Observation samples included sections from the transverse, radial, and tangential planes of wood near the pith and the bark, while cell maceration was performed on each growth ring, from the wood near the pith to the outermost wood. The measurement and analysis of trachea include distribution, diameter, and length, conducted on each growth ring of reaction and opposite wood. Similarly, the measurement and analysis of fibers, including fiber length, fiber diameter, lumen diameter, and cell wall thickness, were also carried out on each growth ring. The anatomical characterization of reaction and opposite wood in Pterocarpus indicus was performed according to IAWA standards. Quantitative observations were followed by statistical analysis, including mean comparison and logarithmic regression. Based on the study, tracheids, trachea, fibers, and xylem parenchyma were observed in each type of section. Fiber cells have thin-bordered pits, while trachea cells have vestured pits arranged alternately. In the radial section, ray parenchyma cells were observed, while in the tangential section, uniseriate ray parenchyma with stratified fiber and ray patterns were seen. In the transverse section, axial parenchyma with aliform, aliform-winged, and banded patterns were observed. Additionally, the safranin used to stain the sections bound more strongly to the fiber cell walls in opposite wood than in reaction wood. This is due to the denser fiber distribution in opposite wood. After qualitative observation, quantitative analysis showed that trachea distribution in each growth ring varied, with the average trachea distribution in reaction wood (earlywood: 2.28 cells/mm², latewood: 2.55 cells/mm²) being lower than in opposite wood (earlywood: 2.34 cells/mm², latewood: 2.66 cells/mm²). Trachea diameter also varied, with the average diameter of trachea in reaction wood (earlywood: 222.25 ?m, latewood: 181.95 ?m) being higher than in opposite wood (earlywood: 198.41 ?m, latewood: 172.77 ?m). The trachea distribution pattern in reaction and opposite wood of Pterocarpus indicus is diffuse in growth rings near the pith, semi-ring-porous in wide growth rings, and ring-porous in narrow growth rings. Trachea length also varied, with an average length of 235.52 ?m in reaction wood and 235.62 ?m in opposite wood. Variations in trachea distribution and dimensions occur because trachea respond to mechanical stress. The fiber cell length from near the pith to near the bark in both reaction and opposite wood increased, while fiber diameter and lumen diameter decreased. The fibers in reaction wood are longer, with an average fiber length of 1224.28 ?m, compared to opposite wood, which has an average fiber length of 1048.88 ?m. This difference is due to the tension in reaction wood, which helps prevent the tree's stem from cracking or breaking. The cell walls of reaction wood fibers are also thicker, with an average thickness of 1.82 ?m, compared to opposite wood, which has an average cell wall thickness of 1.48 ?m. This is likely due to the formation of a gelatinous layer on the cell walls of reaction wood fibers, which generally forms more abundantly in reaction wood fibers than in opposite wood fibers.