Monopodial and sympodial bamboos grown in tropic and sub-tropic countries – A Review

Abstract

Bamboo belongs to the grass family and is an important non-timber forest product in tropic and sub-tropic countries. The global trade of bamboo products is worth billions of dollars and is mainly dominant with monopodial bamboo grown in sub-tropic countries such as China and Japan. Many researchers globally discuss that in addition to species and region, bamboo quality can differ based on its rhizome types because the physiology is different for both monopodial and sympodial bamboo. However, there is a massive competition within the yearly forest products due to the challenges posed by underground root system in agroforestry. This review studied the properties of bamboo with regards to their differences in terms of monopodial and sympodial types of rhizomes. It was found that most of the structural, chemical organic, and mechanical properties are higher in monopodial bamboo, but there is a greater fibre morphology and decay resistance in the sympodial bamboo.

Full Article

Monopodial and Sympodial Bamboos Grown in Tropic and Sub-tropic Countries – A Review

Norul Hisham Hamid,^a,b Mohammad Jawaid,^b,* Ummi Hani Abdullah,^a,b and Taghrid S. Alomar ^c

Bamboo belongs to the grass family and is an important non-timber forest product in tropic and sub-tropic countries. The global trade of bamboo products is worth billions of dollars and is mainly dominant with monopodial bamboo grown in sub-tropic countries such as China and Japan. Many researchers globally discuss that in addition to species and region, bamboo quality can differ based on its rhizome types because the physiology is different for both monopodial and sympodial bamboo. However, there is a massive competition within the yearly forest products due to the challenges posed by underground root system in agroforestry. This review studied the properties of bamboo with regards to their differences in terms of monopodial and sympodial types of rhizomes. It was found that most of the structural, chemical organic, and mechanical properties are higher in monopodial bamboo, but there is a greater fibre morphology and decay resistance in the sympodial bamboo.

DOI: 10.15376/biores.18.3.Hamid

Keywords: Bamboo; Rhizome; Growth; Anatomy; Physical; Mechanical properties; Chemical properties; Decay resistance

Contact information: a: Faculty of Forestry and Environment Universiti Putra Malaysia 43400 UPM Serdang, Selangor, Malaysia; b: Institute of Tropical Forestry and Forest Products Universiti Putra Malaysia 43400 UPM Serdang, Selangor, Malaysia; c: Department of Chemistry, College of Science, Princess Nourah bint Abdulrahman University, Riyadh 11671, Saudi Arabia; *Corresponding author: h_noroul@upm.edu.my

INTRODUCTION

Bamboo is a monocotyledon plant and is classified as sub-family of Bambosoidea in the family of Graminae. Worldwide, bamboo consists of 119 genera and 1500 species under three main tribes, namely, Arundinarieae (temperate woody bamboo), Bambuseae (tropical woody bamboo), and Olyreae (herbaceous bamboo). They are distributed within the tropic and sub-tropic regions from sea level to the alpine, with the altitude or from 47° S° to 50° 30’ N and latitude from sea level to 4300 m (Clark et al. 2015). Bamboo stands exist in all continents except for Europe and Antarctica (Ram et al. 2010; Hagarth and Belcher 2013; Mera and Xu 2014).

Bamboo culms cover about 3.2% (37 million hectares) of the world forest area. Approximately 80% of the bamboo stand and species are distributed in the Asia and pacific regions (Mera and Xu 2014). China owns the largest bamboo forest area (601,000 km²) followed by India (108,630) and Myammar (8950 km²) (Fei et al. 2016). The deforestation that occurs in these countries is relieved by the emergence of bamboo forests and in turn this balances the ecosystem.

A bamboo forest is part of the forest ecosystem, and it acts as an important source of carbon and carbon sink (Li et al. 2003). Bamboo possesses a great advantage of reducing global warming by utilizing the carbon dioxide emission produced from modern vehicles, industries, and population growth. One hectare of bamboo culms is able to absorb more than twelve tons of carbon dioxide per year (Raka et al. 2011), while the dicotyledon trees only absorb slightly lower carbon dioxide, ranging from 1.1 to 9.5 tons per year (Chasan 2019). This is due to the fact that bamboo achieves its maximum growth within a one year and matures within 3 to 4 years for sympodoal bamboo and 7 to 8 years for monopodial bamboo (Razak et al. 2010; Fangchun 2001a,b). Depending on the bamboo culm, the photosynthesis process that produces carbohydrates for the growth and maturation is also involved in nutrient uptake from soils.

The bamboo culm grows toward maturation, and when it gets old, it loses its ability to uptake nutrients from soil. The amount of nutrients or inorganic contents in Gigantochloa scortechinii culm declines from a young age (6 months), toward its old age of 6.5 years (Norul Hisham et al. 2006). The oldest bamboo culm experiences an insufficiency in nutrients and will produce flowers and then die if it is not being utilised for any purpose. Therefore, mature bamboo culm needs to be harvested to allow a new shoot to emerge from the rhizome to produce a new culm. The age-maturation of bamboo culm is important to determine the harvesting cycle of each bamboo culm for production, propagation, and its overall sustainability for further utilization. The making of a specific bamboo product depends on the culm age for its maximum quality. Bamboo shoot as a food is best when it emerges less than 3 weeks from soils (Fangchun 2001b). The quality of bamboo higo products, such as barbeque and chop sticks, are maximum for the bamboo culm aged 1 to 2 years (Hamdan and Mohmod 1992). While the most suitable age for bamboo timber and flooring ranges from 3 to 4 years for sympodial bamboo to achieve its maximum strength (Sattar et al. 1994; Mohmod and Phang 2001; Banik 2015).

A mature bamboo culm as a biological material for human products evolved from traditional to a modern application parallel to human civilization. Historical records show that bamboo was used as fire work and in rockets during the Chinese dynasties (Deluca 2016). Indigenus people in Southeast Asia used bamboo as a rice cooker and in weapons in their daily life. Fei et al. (2016) mentioned that half of the world population utilizes bamboo products such as in housing, biocomposites, mats, chopsticks, charcoal, activated carbon, pulp, shoot, and other applications.

Medicine is another category of a small amount of bamboo products. The Pleioblastus amarus leaves can remedy fever, fidgeting, and lung inflammation (Kiruba et al. 2007). The extracts of Sasa senanensis, Bambusa caulis, and Pseudosasa japonica have anti-cancer activity (Panee 2009; Seki et al. 2010; Kim et al. 2013). In addition, bamboo is reported to have great potential for soil erosion control, water conservation, land rehabilitation, and carbon sequestration (Zhou et al. 2005).

The bamboo industry has evolved from being used as basic tools for domestic requirement to world commodities for international markets. The global bamboo market was about USD 68.8 billion in 2018 (Market Research Report 2019). The most popular product, woven bamboo, represents the largest proportion of global exports, estimated at USD 380 million in 2017 (Inbar 2020). China with the largest bamboo forest area is a main exporter for bamboo products. China’s bamboo industry success is not only related to its culture that has been ever expanding, but the proper selection of bamboo species for a specific product for optimum qualities is the main contribution for success. Norul Hisham et al. (2006) explained that there are thousands of bamboo species worldwide and their properties differ by species, age, location, and other external factors. According to the phenotype, bamboo can be divided into three types of rhizomes, namely monopodial (leptomorph), sympodial (pachymorph), and amphipodial. The different rhizome structure possibly influences its growth, development, and maturation (Fangchun 2001a; Fei et al. 2016).

Despite being in the same tribe, the growth and development phases in monopodial and sympodial bamboo culms may be different due to different rhizome structures. Zhao et al. (2014) made comparison between the micro Ribonuleic acid (mRNA) of monopodial bamboo (Phyllostachys pubescens) and sympodial bamboo (Dendrocalamus latiflorus). In their reports, the rhizome of monopodial bamboo can spread laterally while grown in soil, and can also be separated from the mother plant, while sympodial bamboo grows in clusters within a relatively small range. The result indicates that there are 19,295,759 and 11,513,888 raw sequence reads, in which 92 and 69 conserve miRNAs, as well as 95 and 62 novel miRNAs are identified in P. pubescens and D. latiflorus, respectively. The ratio of high conserved miRNA families in D. latiflorus is more than that in P. pubescens. In addition, a total of 49 and 106 potential targets are predicted in P. pubescens and D. latiflorus, respectively, in which several targets for novel miRNAs are transcription factors that play important roles in plant development. Experiments show that miR397, miR1432, and miR7748 are specifically conserved in the leaf sample of P. pubescens.

Taken together, the comparison between P. pubescens and D. latiflorus indicate that monopodial and sympodial bamboo may share different miRNAs and target genes to have a better adaption for their development in different stages, and stress response in their diverse course of evolution. Therefore, monopodial bamboo requires more self-regulation to adapt to the environment than sympodial bamboo, which might be consistent with the generation of lower conserved miRNAs families. Fangchun (2001a) investigated the physical properties of 96 bamboo species and the mechanical properties of 65 bamboo species from both monopodial and sympodial bamboo. The moisture content, density, shrinkage, tensile, and compression properties vary by species, which originated from different rhizome type. The growth, development, and properties of some bamboo species either from monopodial and sympodial rhizomes may also be influenced by the site condition and climate of a specific area.

The International Network for Bamboo and Rattan (INBAR) proposed priority species of bamboo and rattan that include 20 taxa (species and genera) of particular economic importance and another important 18 taxa (Rao et al. 1998). In this context, the priority is based on its specific uses, and the main criteria for the classification of species-usage is general characteristics, such as diameter, wall thickness, internode length, and overall culm height. The priority species by the culm physical properties, P. pubescens, is categorized as medium to large monopodial bamboo with 10 to 20 m height, 18 to 20 cm diameter, internodes up to 45 cm long, and thick wall up to 2 cm (Rao et al. 1998). The P. pubescens is the most successful bamboo species in China for manufacturing glue-laminated timber flooring.

A similar characteristic in sympodial bamboo such as Dendrocalamus asper with up to 20 to 30 m height, internodes 20 to 45 cm long, diameter of 8 to 20 cm, and thick walls up to 2 cm, is that they are only used as furniture, musical instruments, chopsticks, household utensils, and handicrafts (Rao et al. 1998). The thick wall of D. asper does not give advantage for manufacturing glue-laminated board or flooring in Asian countries. The examples of end products from monopodial and sympodial bamboo species are shown in Table 1 and 2.

Table 1. Example of the Utilization of Monopodial and Sympodial Bamboo in China (Liu et al. 2018)

Table 2. Example of the Utilization of Sympodial Bamboo in Malaysia

Another example is the trial of glue laminated bamboo board and flooring from sympodial bamboo G. scortechinii in Peninsular Malaysia during 1998 to 2001. The G. scortechinii culm has an internode ranging 32 to 50 cm long, 11 to 18 cm in diameter, and 6 to 9 mm in wall thickness (Norul Hisham et al. 2006), which is similar to P. pubescens grown in China. However, after two decades of trial, the quality appearance and marker acceptance of laminated bamboo flooring from G. scortechinii was not comparable to P. pubescens. In the period of 1998 to 2015, two laminated bamboo board factories in Malaysia were closed down due to lack of quality appearance for the local market. Another contributing factor is unsustainability of the material, as most of the stock is obtained in the natural forest and the bamboo plantation is not established at the beginning. This indicates that the quality of laminated bamboo flooring and other biocomposites is not only dependent on the basic and physical characteristics. Other properties, such as chemical, mechanical, machining, and appearance that vary between monopodial and sympodial bamboos, are a collective factor for optimum quality. In view of the above, this review aims to elaborate the properties characterization in monopodial and sympodial bamboos.

RHIZOME

The monopodial rhizome has a long and slender culm with a cylindrical or sub-cylindrical form. Its diameter usually is less than that of the culm coming from it (Fig. 1).

Its internode is longer, relatively uniform in length, rarely solid, typically hollow with interruptions at each node by a diaphragm; nodes in some genera usually elevated or inflated, in others no lateral buds in the dormant state are boat-shaped (McClure 1966). The monopodial bamboo is characterized as having strong frost resistance and is distributed in area of higher latitudes, such as Japan, Korea, Yellow River, and Yangtze Valley where there is a slight winter (Fangchun 2001a).

The sympodial rhizome has 6 to 7 large lateral buds on either side of the thick rhizome proper, and the buds grow up to new bamboos with a short rhizome neck (Fig. 1). The rhizome internodes are broader, long, solid, and asymmetrical, while the nodes are not elevated. The underground rhizome consists typically of two parts: the rhizome proper and the rhizome neck. The neck is basal to the rhizome proper, generally shorter in length and obconical in shape. It connects the new rhizome to the mother rhizome. Rhizomes are usually more or less curve-shaped and rarely straight, with maximum thickness, typically somewhat greater than that of the culm (Liese and Kohl 2015).

Being morphologically different, the monopodial bamboo rhizome can be extended horizontally under the soils depending on the species, and its length ranges from 50 to 70 m for P. heteroxyxla, 90 to 250 m for P. viridis, and 200 to 350 m for P. niagra (Jinghua 2000). Sympodial bamboo rhizome, such as B. tulda, can only be extended under the soils, up to 5.2 m (White and Childers 1945). Due to this capability, monopodial and sympodial bamboo rhizomes are commonly referred to as running and clumping bamboos, respectively. Amphipodial, which is a combination of monopodial and sympodial rhizomes, belongs to the genera including Bashania and Shibataea (Maoyi 2007). These genera originated from Japan.

Fig. 1. Monopodial bamboo and rhizome and sympodial bamboo and rhizome (Redrawn with inspiration from Banik et al. 2015)

SPROUT AND GROWTH

Monopodial Bamboo

The P. nigra var. henosis has the shortest sprouting phase (19 days), followed by P. nidularia (20 days), and P. makinio (25 days) as shown in Table 2. The P. heteroclade has the longest sprouting phase (45 days) among the Phyllostachys genera. The sprouting phase of P. pubescence grown in China (28 days) is quicker than those grown in the USA (44 days). This is reflected by the different site and climate between these countries. The growth phase is quickest for P. nigra (24 days) followed by P. pubescens (31 days) and P. makinoi (32 days) in China (Hwang and Ma 1994; Zhang et al. 1997; Li et al. 2005).

Sympodial Bamboo

The Fargesia spathecea has the earliest sprouting phase (59 days) amongst the sympodial bamboo, followed by F. robusta (80 days) and F. denudate (90 days). D. latiflorus has the longest sprouting phase (180 days) amongst the sympodial bamboo. The growth phase is the quickest for Fargesia robusta (70 days) followed by Dendrocalamopsis oldhani (80 days) and D. latiflorus (90 days) in China (Zhou 1999; Qin et al. 1993; Gao et al. 2000).

Overall

The sprouting and growth phases are significantly shorter in monopodial bamboo (32.7 and 33.2 days) compared to the sympodial bamboo (105.8 and 102.6 days), respectively, from further analysis of the statistical data (Table 3). The bamboo shoot elongation rate within 24 h depends on the genera, species and rhizome. P. reticulate records the fastest growth rate (maximum 120 cm/day) for monopodial bamboo (Ueda 1960), and the rate is same as D. asper for sympodial bamboo (Subsansenee 1994). The growth rate of B. balcooa, D. gigantus, and B. vulgaris are recorded as 77 cm/day, 58 cm/day, and 44 cm/day, respectively (Osmastos 1918; Banik 1993).

Table 3. Sprouting and Growth Phases of Monopodial and Sympodial Bamboos

Mono – monopodial, Sym – sympodial, S.E – South east, N – North, S.W – South west, C- central, W – West, E- East, S – South

Table 4. Statistical Analysis of Sprouting and Growth Phases for Monopodial and Sympodial Bamboos

*** Significant at P < 0.01. The value in the parenthesis is standard deviation.

CULM DIAMETER AND HEIGHT

Most bamboo culm achieves maximum height within one year, without showing any further growth for subsequent years (Liese 1985). The classification of culm diameter and height is useful in helping to identify the growth factors for individual species in different site location, topography, climate, and other conditions (Fangchun 2001a). It is also commonly used to classify bamboo according to its suitable usage (Benton 2015; Liese and Kohl 2015). Fangchun (2001a) classified the bamboo growth according to the average diameter namely: Class 1 (diameter more than 12 cm), Class 2 (10 to 12 cm), Class 3 (8 to 10 cm), Class 4 (6 to 8 cm), and Class 5 (less than 6 cm).

Monopodial Bamboo

The P. nigra var. henonis grown in Central China achieves a maximum height of 400 cm in only 34 days (Li et al. 2005). The culm diameter and height vary with genera and species in different site locations (Table 4). The P. makinoi grown in the Dasi site, West Taiwan records the highest diameter at breast height (DBH), height, and point density (5.9 cm, 11.1 m, and 18767 culm/ha) compared to Jhudong site, West Taiwan (4.7 cm, 10.7 m, and 17567 culm/ha), respectively. The P. pubescence is grown in the Shi Zhua site, Taiwan with a lower temperature (11.5 °C), and higher elevation that has a significantly higher DBH, height, and culm density (10.6 cm, 21.4 m, and 8344 culm/ha) compared to the Hui sun site (6.8 cm, 10.3 m, and 7933 culm/ha), which has temperature and elevation of 20.3 °C and 667 m, respectively (Wang and Chen 2015). This indicates that the P. pubescens prefers the mountain climate with elevation of 1000 to 1500 m.

The majority of the monopodial bamboo (Table 5) species is classified as class 4 and 5, with exception of P. pubescens (Class 2). Physically, P. pubescens is selected for manufacturing laminated flooring and other composite board in China. The quantity of bamboo strips is proportional to the culm diameter. The P. pubescens records the longest culm (21.4 m) for monopodial bamboo. Other monopodial bamboo species produce a culm length less than 12 m (Table 4).

Sympodial Bamboo

Clump size also influences the culm DBH and height as in sympodial bamboo. Generally, the culm’s DBH and height increases with increasing clump size (Table 5). The small (4.5 m²), medium (7.13 m²), and large (9.3 m²) clump sizes of B. stenostachya produce the DBH (8.7 cm, 9.3 cm and 10.2 cm) and height (15.3 m, 17.4 m, and 20.3 m) respectively (Chen et al. 2012). The sympodial bamboos have all the classes as shown in Table 5. The species with diameter class 1 including D. asper, D. latiflorus, G. levis, Melocanna bambusoides, and Oxytenanthera abyssinica. Others, including B. vulgaris var. striata, B. stenostachya, Gigantochloa scortechinii, G. wrayi, and S. grande are classified as class 2, the same as P. pubescens. The D. latiflorus and T. oliveri are recorded as the longest culm (25 m) for sympodial bamboo. This is followed by B. vulgaris var. striata, D. asper, and M. bambusoides (23 m), and lastly, by B. stenostachya, G. ligulata, and S. funghomii (20 m).

Overall

The sympodial bamboo (9.3 cm and 17 m) has a significantly higher DBH and height than monopodial bamboo (5.6 cm and 10.8 m), as shown by the statistical analysis of the data (Table 5). This factor may be due to the fact that most sympodial bamboo are grown in tropical countries that are rich in sunlight and rain for photosynthesis. The starch stored in parenchyma is used for the culm growth. By contrast, most monopodial bamboo is grown in temperate countries with less sunlight, and the starch are stored in the parenchyma that are later used for their sustenance during winter and snow.

Table 5. DBH and Maximum Height of Monopodial and Sympodial Bamboo