Анатомические изменения и свойства древесины aquilaria crassna и gyrinop swalla для применения в лесозаготовках и агролесоводстве

DOI:

Aquilaria crassna and Gyrinops walla are aromatic tree species renowned for their production of agarwood, a highly valued resin used in perfumery, incense, and traditional medicine [5]. A. crassna , commonly known as agarwood, produces resinous heartwood in response to fungal infection, while G. walla , found in Southeast Asia, also yields agarwood. The fragrance industry heavily relies on these trees for their distinctive scent, which drives their commercial significance [5].

The anatomical properties of both A. crassna and G. walla have been described in previous studies, revealing similar structural features that contribute to their fine wood texture. Both species exhibit a diffuse-porous wood anatomy, with vessels evenly distributed across growth rings. The vessels are mostly solitary or occasionally arranged in short radial multiples, and the axial parenchyma is paratracheal, appearing as scanty lines around the vessels. The rays are uniseriate to multiseriate and homogenous, consisting predominantly of procumbent cells. These anatomical features are typical of the Thymelaeaceae family, known for its fine-textured and uniform wood, which influences both workability and aesthetic appeal [1].

The anatomical and mechanical strength properties of these trees are fundamental in determining their suitability for various applications. Anatomical properties, such as cell structure and tissue arrangement, influence the wood’s resilience, strength, and adaptability to environmental conditions [2]. Strength properties, including bending strength, compressive strength, and flexibility, define the timber’s capacity to withstand external forces, making these traits critical for both natural adaptation and practical usage. Understanding these properties is essential not only for the cultivation and for management of A. crassna and G. walla but also for expanding their applications beyond agarwood production, such as in light construction [4; 9].

The economic value of agarwood is substantial, with first-grade agarwood commanding one of the highest commercial values among natural raw materials [11]. Agarwood is sold in various forms, including woodchips, powder, and incense, contributing to its widespread market presence. However, the overexploitation and limited natural distribution of both A. crassna and G. walla pose serious sustainability challenges, threatening the availability of natural agarwood. This highlights the urgent need for sustainable resource management to preserve these valuable species.

This research aims to address the gap in understanding the anatomical and mechanical properties of A. crassna and G. walla , offering insights that can optimize the agarwood industry, innovate fragrance and medicinal applications, and guide sustainable resource management. By examining the wood’s structural characteristics and strength properties, this study informs practices in the wood and fiber industries, aids in climate adaptation, and contributes to conservation efforts. Furthermore, the findings support the development of sustainable cultivation practices, promoting the economic viability of plantations and reducing dependence on wild agarwood sources. Ultimately, the research has broad implications for industries, communities, and environmental conservation, demonstrating the importance of these species in both local and global contexts.

Materials and methods

Study Location. The study was conducted at the State Timber Corporation (latitude 6.81185° or 6° 48’ 43’’ north, longitude 79.88092° or 79° 52’), Battaramulla, Sri Lanka, during the period from August to October 2023.

Sampling. Timber samples were obtained from the Marambekanda Estate, which is managed by Sadaharitha Plantation (Pvt) Ltd, located in Avissawella within the Colombo District of the Western Province, Sri Lanka. The research site, positioned at a latitude of 6° 95’ and a longitude of 80° 20’, falls under the Low Country Wet Zone (WL4) climatic classification. The elevation of the site is recorded at 35.32 meters above sea level. Meteorological data indicate an average annual rainfall of approximately 2262 mm and an average annual temperature of 29°C. The predominant soil type in the area is red-yellow podzolic soil. For the study, five samples were collected from eight-year-old plants of each species.

Species. The common names agarwood and wallapatta are associated with the botanical names Aquilaria crassna and Gyrinops walla , respectively. Both species are classified under the family Thymelaeaceae. Known for their high value, these plants are often cultivated for their aromatic resin. The production of this resin, used in perfumes and incense, is induced naturally or artificially in the wood of these trees.

Wood section cutting. The selected wood samples were soaked in water for two weeks until air spaces inside the wood were occupied by water. Each wood species was cut into blocks measuring 2 cm × 2 cm × 3 cm to prepare microscopic slides. Using a microtome (Model LEICA SM 2000 R), transverse, radial, and tangential sections in the range of 10–15 µm thickness were taken. During the wood section cutting, the piece of timber specimen and knife were soaked in 30% ethanol for 10 minutes to facilitate fine sectioning and prevent infection by microorganisms.

Staining and mounting. Transverse, radial, and tangential sections were mounted permanently using Canada balsam. Using a Petri dish, separated wood sections were dipped in 50% alcohol for 5 minutes to ensure dehydration. They were then flooded in safranin with 50% alcohol for 15 minutes for further removal of the moisture and the color. The wood samples were subsequently rinsed with 70% alcohol for 5 to 10 minutes to facilitate further dehydration and then immersed in 90% alcohol for an additional 10 minutes. Wood sections were again kept with absolute alcohol for 10 minutes for further dehydration (during the process evaporation was avoided with covering). Then wood sections were kept in xylene with absolute alcohol for 10 minutes. Milkiness occurs at this stage, indicating incomplete dehydration. Thus, samples were again rinsed in absolute alcohol and xylene for

10 minutes. Then wood sections were mounted with Canada balsam to fix the wood sections. Finally, the slides of wood sections were observed through the microscope. Transverse (T.S.), tangential (T.L.S.), and radial (R.L.S.) wood sections were placed on a slide in the below manner. Slides were kept in the laboratory of the State Timber Corporation.

Anatomical identification of wood species. Quantitative wood anatomical features such as mean diameter of vessel lumina, vessels per square millimeter, ray height, ray width, rays per 25 square millimeters, and fiber length were measured. Qualitative parameters such as vessel shape and arrangement were also recognized. One set of slides from each species was employed to take the measurements. All of the quantitative and qualitative information on the anatomical characteristics was tabulated.

Microscopic examination. Anatomical observations on quantitative and qualitative features were made under a light microscope at 4 × 1 0 magnification. Measurements and anatomical images were made with Micrometrics SE Premium 4 Software available at the research division of the State Timber Corporation. Quantitative wood anatomical features and qualitative wood anatomical features were measured according to the IAWA list (1989).

Anatomical observation with a handheld digital microscope. Microscopic images of cross-sectional wood samples from each species were captured and analyzed using a handheld digital microscope. Observations were made at 20 × magnification, and the numbers of rays and vessels per 25 mm² wood area were recorded.

Determination of the density. Determination of the density of wood was carried out using Archimedes’ principle for various species. Timber samples, each measuring 2 cm × 2 cm × 2 cm, were cleaned of impurities, including sawdust and mud, and labeled accordingly. To saturate the vessels with water, the samples were submerged in water for approximately 30 minutes. The weight of a beaker filled with water (W1) was measured using an electronic balance. After three days, the samples were placed in a desiccator to stabilize the temperature, and their dry weights were recorded.

The samples were then oven-dried at 103°C for three days to ensure all moisture was removed. A water-saturated sample was subsequently immersed in the beaker at a consistent depth using a thin stick attached to a stand, and the final weight of the beaker (W2) was noted. The wet weight of the wood sample was calculated using a specific equation (1):

Timber weight (W) = Final beaker weight (W2) – – Initial beaker weight (W1). (1)

To determine density at 0% moisture level, equation (2) was used:

Density at 0% moisture =

= Oven dry weight of timber sample *      (2)

Weight of timber sample (W)

x Density of Water (1000 kgm ’).

Density at 12% moisture level was determined using equation (3):

Density at 12% moisture level =

= Density at 0% moisture level ) x x 112( kgm '3).

Determination of the moisture content of wood samples. The moisture content of the samples was measured at 12% condition using a moisture meter available at the Wood Science Laboratory in the State Timber Corporation.

Fiber length measurements. Fiber length measurements were conducted to assess the anatomical characteristics of Aquilaria crassna and Gyrinops walla . Samples were prepared by macerating thin wood sections in a solution of glacial acetic acid and hydrogen peroxide (1:1 ratio) at 60°C for 24 hours to separate individual fibers. The macerated fibers were then washed thoroughly, mounted on glass slides, and examined under a trinocular microscope (Accu-scope 3000 series). Fiber lengths were measured using Micrometrics SE Premium 4 Software, with at least 30 fibers randomly selected per sample to ensure statistical reliability. The measurements provided insights into the structural attributes influencing the wood’s mechanical properties and potential applications.