Anatomical characteristics, fibre morphologies, and densities of six rattan species from Malaysia

Abstract

The anatomical characteristics, fibre morphologies, and densities were evaluated for six rattan species, i.e., Calamus manan, Calamus ornatus, Calamus ridleyanus, Calamus crinitus subsp. sabut, Korthalsia scortechinii, and Korthalsia tenuissima from the Forest Research Institute in Malaysia. Rattan samples of about 5 to 7 cm were cut at the middle portion of the internodes of a mature stem for assessment. The results allowed differentiation between the genera Calamus and Korthalsia based on anatomical characteristics such as the type of vascular bundle, ground tissue, and the presence of the ‘yellow cap.’ The fundamental properties of C. manan, including longer fiber length, thickest fibre wall, and higher density compared to other species, signified the superior quality of this species. Based on the density result, the study of other species of rattan would also find potential for furniture, decorations, and craft purposes.

Full Article

Anatomical Characteristics, Fibre Morphologies, and Densities of Six Rattan Species from Malaysia

Nordahlia Abdullah Siam, Alia Syahirah Yusoh, Asniza Mustapha, Nur Syauqina Syasya Mohd Yusoff, Azharizan Mohamad Norizan, Wan Tarmeze Wan Ariffin, and Mohd Khairun Anwar Uyup *

The anatomical characteristics, fibre morphologies, and densities were evaluated for six rattan species, i.e., Calamus manan, Calamus ornatus, Calamus ridleyanus, Calamus crinitus subsp. sabut, Korthalsia scortechinii, and Korthalsia tenuissima from the Forest Research Institute in Malaysia. Rattan samples of about 5 to 7 cm were cut at the middle portion of the internodes of a mature stem for assessment. The results allowed differentiation between the genera Calamus and Korthalsia based on anatomical characteristics such as the type of vascular bundle, ground tissue, and the presence of the ‘yellow cap.’ The fundamental properties of C. manan, including longer fiber length, thickest fibre wall, and higher density compared to other species, signified the superior quality of this species. Based on the density result, the study of other species of rattan would also find potential for furniture, decorations, and craft purposes.

DOI: 10.15376/biores.20.1.57-69

Keywords: Rattan species; Anatomical characteristics; Fibre morphology; Density; Vascular bundle

Contact information: Forest Research Institute Malaysia, 52109 Kepong, Selangor, Malaysia; *Corresponding author: mkanwar@frim.gov.my

INTRODUCTION

Rattans, a collection of spiny and climbing palms, hold significant importance as non-timber forest products within tropical and subtropical forest ecosystems. They fall under the subfamily Calamoideae of the Arecaceae family (Dransfield 1986, 1992). Worldwide, there are approximately 22 genera and over 650 rattan species (Govaerts et al. 2014). Out of these, only four genera, i.e., Calamus, Daemonorops, Korthalsia, and Plectocomia are commercially traded (Jiang and Peng 2007). Rattan, characterized by its long, tough, slender stems, is a versatile plant resource primarily found in tropical rainforests. It holds substantial economic value, making it a material of considerable potential in the construction industry (Akpenpuun et al. 2017). Malaysia stands out as one of the leading rattan producers globally, with a burgeoning rattan industry contributing significantly to the country’s economic growth. Ranked second only to Indonesia in the rattan industry, Malaysia has seen robust development in this sector (Razak et al. 2019). Rattan cane is extensively utilized for various purposes, including furniture, ropes, decorative items, mats, housing, baskets, crafts, and construction (Yang et al. 2020). According to Wan Tarmeze et al. (2018), larger diameter rattans find application in crafting furniture, carpet beaters, and walking sticks, whereas smaller diameter ones are employed in creating mats, baskets, marine traps, animal cages, and coarse wickerwork.

Numerous studies have been conducted to examine the anatomical properties of rattan for the purpose of classification and identification (Weiner and Liese 1993; Krisdianto and Jasni 2005; Krisdianto et al. 2018; Dewi et al. 2019). Furthermore, Yu et al. (2023) emphasized that an examination of the anatomical characteristics of rattan, including vascular bundle diameter, vascular bundle frequency, and tissue proportion was undertaken to observe their correlation with other important properties, i.e., density, shrinkage, and mechanical properties. In contrast, study on the anatomical characteristics, such as fibre morphology, is also important as an indicator to the other properties and suitability for the potential product (Xu et al. 2014). Fibre length and fibre wall thickness are highly related to the density and strength, where longer and thicker fibres are related to the higher density and strength (Dewi et al. 2019; Yang et al. 2020; Sheikh et al. 2022). Hence, a comprehensive understanding of anatomical characteristics and density is pivotal, as it has implications for other important properties and final product distinctive features.

Rattan holds significant importance as a non-timber forest product in Malaysia. Dransfield (1992) documented 106 species from 8 genera in Peninsular Malaysia, with Sabah and Sarawak reporting approximately 79 and 105 species, respectively. Despite this diversity, only about 20 species, including C. manan, C. tumidus, C. caesius, C. peregrinus, C. scipionum, C. ornatus, and Korthalsia rigida, are extensively used commercially in Malaysia (Abd Razak et al. 1995). There is a belief that numerous potential rattan species in Malaysia remain unexplored for their possible commercial applications. This is primarily because most rattan species in Malaysia lack essential data on their anatomical, physical, and mechanical properties, which are crucial indicators for determining their suitability for various applications.

Thus, the current study focuses on six rattan species, encompassing Calamus manan, Calamus ornatus, Calamus ridleyanus, Calamus crinitus subsp. sabut, Korthalsia scortechinii, and Korthalsia tenuissima. The objectives of the research are to investigate fundamental properties, including anatomical characteristics, fibre morphology, and density. It is hoped that these basic properties will be useful to the furniture and handicraft industry to explore suitable products from the rattan species. As stated by Razak et al. (2010, 2016) rattan is of great economic importance in handicraft and furniture manufacturing because it is rich in fibre, possesses suitable toughness, and is easy to work with. Additionally, the anatomical characteristics information from this present study could also aid in the identification of rattan.

MATERIALS AND METHODS

Field Sampling

Six species of Malaysian rattan, i.e., Calamus manan (rotan manan), Calamus ornatus (rotan dok), Calamus ridleyanus (rotan kerai), Calamus crinitus subsp. sabut (rotan cincin), Korthalsia scortechinii (rotan dahan semut), and Korthalsia tenuissima (rotan dahan tikus) were obtained from Forest Research Institute Malaysia (FRIM, Kepong, Selangor, Malaysia). Rattan was identified in the field based on morphological traits, including its habits, leaves arrangement and shape, ocrea, flagella, inflorescence, knee, spine, and fruits. This identification process was conducted by trained and expert botanists to accurately identify the species for this research.

Three rattan canes from each species were selected and harvested. The rattan canes were cut at approximately 20 cm above the ground level. The upper leafy portion of each sample was removed, and samples of about 5 to 7 cm were cut at the middle portion of the internodes of a mature stem and packed in polythene bags for further processing in laboratory. Assessments on the anatomical characteristics, fibre morphology, and density were tested approximately at 12% moisture content. Moreover, anatomical study was also conducted from the outer and inner parts of the bamboo culm.

Determination of the Anatomical Characteristics, Fibre Morphology, and Density of Rattan

The anatomical characteristics were examined following the procedure outlined by Weiner and Liese (1993). Rattan sample blocks were cut into sections measuring 10 mm × 10 mm × culm wall thickness. Subsequently, these blocks were boiled in distilled water until the rattan samples softened. Sections, 25 µm in thickness, were then cut using a sledge microtome. Each section underwent staining with aqueous safranin-O, followed by washing with 50% ethanol and dehydration through a series of ethanol solutions with concentrations of 70%, 80%, 90%, and 100%. Then, the thin wood sections were cleaned twice using xylene solution, before mounting on the glass slides. Finally, a drop of Canada Balsam was applied at top each section, covered with a cover slip, and the slides were oven-dried at 60 ºC for three days.

For assessing fiber morphology, rattan samples of 10 mm × 10 mm × culm wall thickness were chipped into matchstick-sized pieces. These splits were subjected to maceration using a mixture of 30% hydrogen peroxide and glacial acetic acid (1:1 ratio) at 45 °C (Weiner and Liese 1993) for 2 to 3 h, until all lignin was dissolved, leaving the cellulose fibres appearing whitish. After thorough washing with distilled water, the cellulose fibres were retained in vials, gently agitated for proper separation. Vials, half-filled with distilled water and securely capped, were then used to spread the macerated fibres on a glass slide, adding drops of safranin-O, and covering with a cover slip.

Quantitative measurements of fibre length, vascular bundle, metaxylem, phloem, fibre and lumen diameter, and cell wall thickness were conducted from the slides using an optical microscope (Olympus Corporation, Tokyo, Japan). Vascular bundle distributions were determined by counting the number of bundles per mm² on a cross section. Fibre wall thickness was calculated by subtracting the fibre lumen diameter from the fibre diameter and dividing by two. The anatomical terminology adheres to the descriptions provided by Weiner and Liese (1988, 1990, and 1993). For all the measurements 25 readings were taken randomly.

The density was determined in accordance with BS 373 (1957). Discs approximately 20 mm thick were cut from the rattan samples. There were 20 replicates used for density determination. Samples were initially weighed on a balance with 0.001 g accuracy. Calculation used for the density is based on Eq. 1,

(1)

where W_o denotes oven-dry weight (kg), and V_g is green volume (m³)

Statistical Analysis

Statistical analysis was performed using SAS software (SAS Inc., version 9.1.3, Cary, NC, USA). A one-way analysis of variance (ANOVA) was conducted to determine whether the differences in means were significant. If the differences were significant, the least significant difference (LSD) test was used to determine which of the means were significantly different from one another.

RESULTS AND DISCUSSION

Anatomical Characteristics of Rattan

The epidermis layer is one of the anatomical characteristics that could be used to distinguish plant rattan to the species, genera, and family level (Ebanyenle and Oteng-Amoako 2003; Krisdianto et al. 2018; Dewi et al. 2019). Epidermis is the outermost part of the rattan stem, consisting of unlignified parenchyma cells and covered by a siliceous layer (Weiner and Liese 1988). The thicknesses of the epidermis layer of six rattans are given in Table 1. The obtained results, indicate a significant difference in epidermal thickness among the studied species, with C. manan exhibiting the thickest epidermal layer of 50.8 µm. Whereas the thicknesses of K. tenuissima, K. scortechinii, C. ridleyanus, C. ornatus, and C. crinitus subsp. Sabut’s epidermis layer were 43.6, 40.0, 36.4, 34.4, and 24.0 µm, respectively. The results were comparable with previous studies by Krisdianto et al. (2018) and Dewi et al. (2019).

According to Weiner and Liese (1988) and Krisdianto et al. (2018), arrangement of fibre bundles in the peripheral area could also be diagnostics features in rattan identification. The fibre bundles are arranged in one layer with no specific pattern in the peripheral area observed in all six species studied (Figs 1a and 2a). This observation was similar with the finding by Krisdianto et al. (2018) who also found fibre bundles in the peripheral area in nine species of Indonesian rattan, which are arranged in one or two layers. However, it was contradicted with the study by Dewi et al. (2019) who reported there was no fibre bundle found in the peripheral zone in their study of six Calamus species.

The vascular bundles were embedded in the ground parenchyma. As is typical, the inner vascular bundles exhibited a greater diameter and lower frequency compared to those in the outer part of the stem (Yu et al. 2023). These vascular bundles comprised metaxylem, protoxylem, phloem, and fiber sheath. The variability in vascular bundle characteristics can serve as distinctive features at the species, genera, and family levels of rattan. These features encompass both quantitative and qualitative aspects. The quantitative parameters include the diameter and frequency of vascular bundles, as well as the diameters of metaxylem, protoxylem, and phloem. Additionally, the number of cells in the phloem and protoxylem within the vascular bundle can be diagnostic features for distinguishing rattan taxa (Weiner and Liese 1993; Krisdianto et al. 2018; Dewi et al. 2019).

The results of the vascular bundle, metaxylem, protoxylem, and phloem analysis are presented in Tables 1 and 2. Significantly different results were observed within the six rattan species. C. manan exhibited the largest vascular bundle diameter in both the outer and inner parts of the rattan stem, while having a lower vascular bundle frequency. Conversely, C. ridleyanus showed the smallest diameter and higher frequency of vascular bundles. Additionally, larger metaxylem was observed in C. manan. There was an absence of tyloses in the metaxylem of all six species studied (Table 3). Previous studies by Mathew and Bhat (1997), Renuka et al. (2010), Sharma et al. (2018), and Selim and Himu (2021) reported tyloses-like structures present in metaxylem vessels of certain rattan species, which were C. palustris, K. rogersii, Plectocomia bractealis, and C. meghalayensis. The larger diameter of metaxylem and absence of tyloses as observed in this study, align with the findings of Sint et al. (2011), suggesting that these characteristics may contribute to the ease of treatment of the species.

Furthermore, larger protoxylem was observed in C. ornatus and K. scortechinii, while the largest diameter of phloem was found in K. tenuissima. The results regarding vascular bundle, metaxylem, protoxylem, and phloem diameter, as well as the vascular bundle frequency in mm², are consistent with previous studies by Weiner and Liese (1993) and Ebanyenle and Oteng-Amoako (2003).

In contrast, the important qualitative characteristics of the vascular bundle that could be used for the rattan identification is the vascular bundles type. As described by Weiner and Liese (1993), from the cross section of rattan, there were four types of vascular bundles that were type A (comprising one phloem field and one metaxylem vessel), type B (comprising two phloem fields and one metaxylem vessel), type C (comprising one phloem field and two metaxylem vessels), and type D (comprising two phloem fields with uniseriate and biseriate sieve tubes and one metaxylem vessel). Based on the observation of microscopic anatomical characteristics from the cross section, the six species of rattan, i.e., C. manan, C. ornatus, C. ridleyanus, C. crinitus subsp. sabut, K. scortechinii, and K. tenuissima show the type B vascular bundle with one metaxylem and two phloem (Figs. 1b to 1e and 2b, 2c). The analysis of all six species reveals that the number of phloem cells ranges from 4 to 6 cells, and the number of protoxylem cells ranges from 3 to 5 cells (Table 2).

Another diagnostics characteristic that can distinguish the rattan taxa is the ground tissue. The ground tissue consists of isodiametric parenchyma cells with simple pits. Three forms can be distinguishing in a cross section: type A (cells are weakly branched leaving regular rounded intercellular spaces between them, “jigsaw puzzle-like”), type B (smaller, rounded cells with irregularly shaped intercellular spaces, “pebble-like”), and type C (thin-walled cells, large and round with relatively small intercellular spaces, “net-like”). Whereas, when viewed longitudinally, types A and B appear like ‘stacks of coins,’ type C shows short and elongated cells oriented perpendicularly to each other. In accordance with the findings, observation on the cross section of the genus of Calamus, i.e., C. manan, C. ornatus, C. ridleyanus, and C. crinitus subsp. sabut shows the type A ground tissue (Fig. 1f). The type B ground tissue was found in the genus of Korthalsia, i.e., K. scortechinii and K. tenuissima (Fig. 2d). All six species show ‘stacks of coins’ of ground tissue in the longitudinal section (Figs. 1g and 2e). In the longitudinal section, the ground parenchyma of all species studied contains reddish cell contents (Figs. 1g and 2e), which were described as tannins by Tomlinson (1961), Siripatanadilok (1974), and Teoh (1978). This finding was also described by Weiner and Liese (1988) in the study of genus Calamus, Daemonorops, and Korthalsia.

Table 1. Epidermis Layer and Vascular Bundle Characteristics of Six Rattan Species of Malaysia

Values in parentheses are standard deviations; cell values differing by a letter in the superscript in each column are significantly different at 0.05

Table 2. Metaxylem, Protoxylem, and Phloem Characteristics of Six Rattan Species of Malaysia

Values in parentheses are standard deviations; cell values differing by a letter in the superscript in each column are significantly different at 0.05

The rattan fibre sheath is found on the vascular bundle, and it is formed as a ‘horse-shoe’ shape in all six species studied (Figs. 1b to 1e and 2b, 2c). As stated by Liese (1988, 1990, and 1993) the fibre sheath is normally ‘horse-shoe’ shaped. According to Siripatanadilok (1974) and Teoh (1978), another diagnostic feature that can distinguish the rattan taxa was the ‘yellow caps’. This characteristic of ‘yellow caps’, i.e., fibre sclereids at the outer side of the fibre sheath of the first vascular bundles below the cortex. The ‘yellow caps’ get their name by the striking appearance of those features. The ‘yellow caps’ characteristics are present in the species of the genus of Korthalsia i.e., K. scortechinii, and K. tenuissima (Fig. 2a). Whereas these characters are absent in the species of the genus Calamus, i.e., C. manan, C. ornatus, C. ridleyanus, and C. crinitus subsp. sabut. The silica ‘star-like’ form located in the parenchyma cells (Figs. 1h and 2f) was present in all six species studied. This finding was similar to the study by Liese (1993) and Abasolo et al. (2001).

The presence of the silica could affect the processing of the rattan because the particles of silica have an abrasive effect on the saw teeth, producing rapid blunting of cutting edges and heating of the saw blade (Abasolo et al. 2001).

Based on the results obtained, the quantitative anatomical characteristics, i.e., type of vascular bundle, type of ground tissue, and presence of ‘yellow cap’ could be diagnostic features to distinguish rattan to the genera level. This study shows that the genus of Calamus could be differentiated from Korthalsia based on the anatomical characteristics as shown in Table 3. The genus Calamus (Figs. 1a through h) was observed with type B vascular bundle, type A ground tissue, and absence of ‘yellow cap’. Moreover, type B vascular bundle, type B ground tissue, and presence of ‘yellow cap’ was found in the genus of Korthalsia (Figs. 2a through f). The resemblances and connections identified through these anatomical characteristics align closely with the taxonomic classifications suggested by Uhl and Dransfield (1987) and Weiner and Liese (1988, 1990, and 1993).

Fig. 1. Anatomical characteristics of the genus Calamus: a) Cross section (4x): Epidermis layer and fibre bundle (arrow); b) through e) Cross section (10x): Vascular bundle type B that consists of two phloem fields (Ph) and one metaxylem vessel (M), absence of tyloses in metaxylem, Protoxylem (Pr) and fibre sheath ‘horse-shoe’ shaped (arrow); f) Cross section (10x): Type A ground tissue “jigsaw puzzle-like” (GT); g) Longitudinal section (10x): Ground tissue (GT) ‘stacks of coins’ and reddish cell contents (arrow); and h) Longitudinal section (40x): Silica of ‘star-like’ form (arrow). a, b, and h: C. manan; c and g: C. ornatus; d: C. ridleyanus; e and f: C. crinitus subsp. Sabut; Scale bars = 10 μm