Anatomical characteristics of Gigantochloa scortechinii bamboo rhizome in relation with hydraulic conductance

Mohamed, J., Abdul Hamid, H., Nuruddin, A. A., and Nik Abdul Majid, N. (2019). "Anatomical characteristics of Gigantochloa scortechinii bamboo rhizome in relation with hydraulic conductance," BioRes. 14(4), 9082-9099.

Abstract

Structural development and modification of bamboo culm’s anatomical characteristics occur during the maturation period. This process affects the conductivity efficiency in individual bamboo culms (above ground). The present study clarified this process in the sympodial type of bamboo rhizome (belowground). This study aimed to observe the anatomical characteristics of Gigantochloa scortechinii rhizome, examine their relationship with different study sites and rhizome ages, and investigate their relationship with hydraulic conductance. Destructive sampling on four consecutive rhizomes was conducted using a selective random sampling method. All rhizome anatomical characteristics were significantly different between study sites except parenchyma diameter, parenchyma lumen diameter, and fiber cell wall thickness. The results also indicated that the vascular bundle diameter, parenchyma diameter, parenchyma lumen diameter, parenchyma cell wall thickness, fiber diameter, fiber cell wall thickness, and fiber length increased with age, but radial to tangential ratio decreased with age. All measured characteristics including the conductance elements had no relationship with hydraulic conductance, except parenchyma diameter and parenchyma lumen diameter. The sizes parenchyma diameter and lumen diameter did not imply a determinant factor in hydraulic conductance. Further studies on rhizome chemical attributes should be carried out to isolate the cause of decreasing hydraulic conductance.

Download PDF

Full Article

Anatomical Characteristics of Gigantochloa scortechinii Bamboo Rhizome in Relation with Hydraulic Conductance

Johar Mohamed,^a,* Hazandy A. Hamid,^a,b Ahmad A. Nuruddin,^a,b and Nik M. N. A. Majid ^a

Keywords: Fiber; Parenchyma; Phloem; Vascular bundles; Xylem

Contact information: a: Institute of Tropical Forestry and Forest Products, Universiti Putra Malaysia, UPM, Serdang, Selangor, 43400 Malaysia; b: Faculty of Forestry, Universiti Putra Malaysia, UPM, Serdang, Selangor, 43400 Malaysia; *Corresponding author: joe5587_forr@yahoo.com

INTRODUCTION

The quality and health of a bamboo stand can be quantified based on the number of culms and age ratio in a clump, maximum growth of morphometric parameters, vigor, and physiological activity (Azmy et al. 1997; Ding et al. 1997; Banik and Islam 2005). The quality and health of stand in a clump have a close relationship with rhizome growth. Rhizomes are generally subterranean and form as the foundational organ for bamboo species by allowing rapid growth at the beginning of a new growing season. Rhizomes are important for nutrient uptake, storage, water absorption and conductance, and the vegetative reproduction system (Li et al. 1998; Liese 1998).

The vegetative reproduction strategy in sympodial bamboo species is to form a large number of rhizomes that are interconnected with each other and hence enable sustainable production. The growth performance, productivity, and life cycle of an individual rhizome in a bamboo clump are strongly related to the ontogenetically and physiologically age-related factors. For example, a new bamboo sprout in a 20-year-old bamboo clump is ontogenetically old but it is physiologically young (Londona 1992; Liese and Weiner 1996; Schweingruber 2007). The growth performance of new sprouts, however, solely depends on the stimulation of rhizome buds (encompass precipitation, relative humidity, soil moisture, and soil fertility) and the sources of energy and nutrients from its interconnected rhizomes. The new sprout has neither photosynthetic leaves nor a rooting system to ensure its rapid elongation (Zhang et al. 1996; Rodrigues et al. 2003).

Structural development and modification of the bamboo culm’s anatomical characteristics occur during the maturation period (Fujii 1985; Alvin and Murphy 1988; Abd-Latif 1996; Liese and Weiner 1996; Londono et al. 2002; Gan and Ding 2005; Wahab et al. 2006). These changes include the thickening of the cell wall, deposition of additional lamella, and lignification that decreases the functional efficiency of conductance elements. The conductance elements must function for several years without secondary meristem. This leads to a breakdown in the conducting systems and dying of individual culms, both above and below ground.

This study examined the rhizome anatomical characteristics of Gigantochloa scortechinii Kurz ex Munro, including their relationship with different study sites, rhizome ages, and their relationship with hydraulic conductance.

EXPERIMENTAL

Sampling

Sampling was conducted at three different locations in Peninsular Malaysia (Table 1). Sampling was conducted using selective random sampling from healthy clumps of Gigantochloa scortechinii Kurz ex Munro. Infertile and congested clumps were ignored. Three clumps were selected for three replicates. Four consecutive rhizomes from each clump were selected, i.e., new sprout (estimated to < one month), young (estimated to one year), premature (estimated to two years), and mature (estimated to three years) (Mohamed et al. 2019). The age estimation was based on the characters of culms (Banik 1993) and the number of rhizomes in a consecutive rhizome from the new sprout (Liese 1998). Only a complete set (four consecutive rhizomes) of a sectorial rhizome with complete plant parts (above and below ground) were chosen.

Determination of Anatomical Characteristics

Fresh samples were cut and sized (10 mm × 10 mm × 10 mm); (length × width × height) prior to examine using a LEO 1455 variable pressure scanning electron microscope (VPSEM; Oberkochen, Germany). The cross section (XS) cubes were prepared using a microtome. The cubes were oven-dried at 60 °C until a constant weight was reached to avoid the presence of steam when examined using the VPSEM. The sample was evaporatively coated using a sputter coater to obtain conductivity without affecting or reduce charging during observation. This method can provide an original figure from un-modified samples; it is cheaper and less time consuming than a conventional scanning electron microscope (PEO 1996).

The anatomical characteristics such as conducting elements, ground tissue, and supporting elements were observed. This study was conducted at the Microscopy Unit, Institute of Bioscience, Universiti Putra Malaysia, Serdang.

Table 1. Information of Three Different Study Sites

Determination of Fiber Length

Fresh sample blocks (10 mm length × 10 mm width × 20 mm height) were prepared before being chipped into matchsticks of 2 mm × 2 mm × 20 mm (length x width x height). The splints were boiled for 6 h. The splints were heated at 85 °C in a solution of 1.5 g of sodium chlorite dissolved in 25 mL distilled water and eight drops of acetic acid for several hours until the splints turned white in color. The white splints were washed carefully with distilled water to remove the solution.

After maceration, splints were stained with safranin-O to contrast the fibers. Distilled water in the splints was dehydrated through an alcohol series of 50%, 70%, 95%, and absolute ethanol for 2 min in each solution. The splints were washed with xylene and mounted on a 25 mm × 75 mm slide. Two drops of Canada balsam were introduced, and samples were dried in an oven at 60 °C for three days. Fibre length was examined under an Olympus SZX-ILLK200 stereomicroscope (Tokyo, Japan). This study was conducted at Laboratory of Biocomposite Technology, Institute of Tropical Forestry and Forest Products, Universiti Putra Malaysia, Serdang.

Determination of Hydraulic Conductance

Culms at selected rhizomes were felled at the culm base and connected to a high-pressure flow meter (HPFM) with a water-tight seal before hydraulic conductance wasmeasured. Water was placed under pressure by compressed air that was controlled with a pressure regulator into the culm base opposite to the normal water flow during plant transpiration. This routine was conducted with rapidly changing the delivery pressure, P (MPa), simultaneously measuring water flow, F (kg s^-1), and hence hydraulic conductance was estimated from the slope of the F versus P plot (Tyree et al. 1994; 1995). The untested culms and belowground parts were avoided, not subjecting them to any cuts or major injuries, so as to reduce the degree of disturbance of the interconnected rhizome system.

The hydraulic conductance trend inside the belowground system where four rhizomes connected consecutively (as a rhizome system) can be used as a measure of their resistance inside. In the present study, the HPFM was used instead of another method (such as evaporative flux and thermal dissipation probe method) because the HPFM permits the determination of hydraulic conductance in a short time, allows determination while the water flows in state of reverse direction, and could reduce the error factors (such as osmotic changes and transpiration of the aboveground part) (Tyree et al. 1995; Tsuda and Tyree 1997; 2000; Do and Rocheteau 2002).

Statistical Analysis

The normality and homogeneity test of variances were performed before analysis using Univariate analysis of variance. Two factors (study site and rhizome age) were involved in the analysis with a total samples, n = 84. An equal sample, n=28 for each study site and n = 21 for each rhizome age, were measured and analyzed. The relationship between anatomical characteristics with each study site, rhizome age, and hydraulic conductance was analyzed using bivariate (Pearson) correlation. The statistical analysis was conducted using IBM SPSS statistics software version 21.0 (Armonk, NY, USA).

RESULTS AND DISCUSSION

Vascular Bundles Distribution

The vascular bundles size and distribution were anecdotally observed to change continuously from inside towards the periphery of the rhizome wall (Fig. 1a, 1b, and 2a). Twisted small vascular bundles between larger vascular bundles were observed (Fig. 2d, 2e, and 2f). Regardless of the study site and rhizome age, the vascular bundle distribution ranged from 62 to 68 bundles cm^-2. Table 2 shows that the vascular bundle distribution was significantly different (p < 0.05) between study sites, which could be related to the intrinsic conditions such as altitude, precipitation, and the disturbance level.

Fig. 1. Transverse section of rhizome wall with lateral buds (a), and lateral bud (b)

Furthermore, the vascular bundle distribution per centimeter square at Ayer Hitam FR was significantly different from those at Amanjaya and Kenaboi FR (Table 3). These results could be related to the smaller size and thinner wall (data not shown) of rhizomes at Ayer Hitam FR compare to rhizome at Amanjaya and Kenaboi FR. These results implied that the rhizome at Ayer Hitam FR formed in an immature planted clump. The morphology of bamboo such as height and diameter of new individual culms (rhizome in this study) increases over consecutive years after planted (Liese and Wiener 1996). Vascular bundle distribution, however, was not significantly different with rhizome age (Table 2). The results in Table 4 indicate that no significant correlation was found between vascular bundle distributions with rhizome age, which implied that the number of vascular bundles does not increase or decrease when rhizome age increases.

Fig. 2. Vascular bundles. (a) Sizes and distribution differ from inside towards the periphery,

(b) with two fiber sheath, (c) with one fiber sheath, (d, e) twisted small vascular bundle between the main vascular bundle, and (f) transverse section of twist angle of a small vascular bundle

Vascular Bundles Diameter

In general, the vascular bundle diameter ranged from 450.25 to 994.20 µm. The large variation in vascular bundle diameter could be due to its position in the rhizome wall zonation (Fig. 1a and 1b) and also influenced by two types of vascular bundles developed (Fig. 2b and 2c). The vascular bundle diameter was highly significantly different (p < 0.01) with study site and rhizome age (Tables 2 and 3). There was no significant difference between vascular bundle diameter with the interaction of study site and rhizome age. The results in Table 4 indicate the vascular bundles diameter had a weak negative relationship (r = -0.246) with study site. A moderate positive relationship (r = 0.343) was found between vascular bundle diameter with rhizome age, which indicates that the diameter slightly increased with rhizome age.

Radial to Tangential Ratio and Protoxylem Diameter

Regardless of the study site and rhizome age, the radial to tangential ratio ranged from 1.60 to 2.19. Tables 2 and 3 show that radial to tangential ratio was significantly different (p < 0.05) with study site, and highly significantly different (p < 0.01) with rhizome age. However, the radial to tangential ratio was not significantly different with the interaction of study site and rhizome age. There was no significant correlation (r = 0.061) between the ratio with study site, but there was a strong negative correlation (r = -0.611, p < 0.01) between the ratio with rhizome age. This result contradicted the study by Wang et al. (2016), where the ratio was not significantly different with age.

Table 2. Summary Analysis of Variance on Anatomical Characteristics and Hydraulic Conductance of G. scortechinii Rhizome

Note: S.O.V = source of variation; S = site; A = age; DF = degree of freedom; ns = not significant (F; p > 0.05, * = significant (F; p < 0.05), ** = highly significant (F; p < 0.01)

Table 3. Duncan’s Multiple Range Test on the Effects of Site and Age on Anatomical Characteristics and Hydraulic Conductance

Note: Mean values with the same letter in the same row at each factors are not significant different (F; p > 0.05); ± = standard error, FR = Forest Reserve

The SEM images show that the vascular bundles of G. scortechinii rhizome consists of both one (Fig. 3a) and two (Fig. 3b) protoxylem, which is in agreement with a previous study by Abd-Latif (1996) on G. scortechinii culms. Regardless of the study site and age, the protoxylem diameter was between 30.45 and 39.19 µm. The protoxylem diameter was significantly different (p < 0.01) between study sites, but there was no significant difference with rhizome age (Tables 2 and 3).

Table 4 indicates a moderate negative relationship (r = -0.413) between protoxylem diameter and study site. A larger average protoxylem diameter was found at Kenaboi FR, followed by Amanjaya FR and Ayer Hitam FR (Table 3). Thus, the protoxylem diameter is more likely affected by intrinsic study site conditions rather than age-related factors. The modifications during protoxylem maturation occur in the cell wall of rings, where thickening and lignification occur throughout the year (Liese 1987; Yoshizawa et al. 1991).

Table 4. Correlation Coefficient Analysis of Anatomical Characteristics with Site, Age, and Hydraulic Conductance

Fig. 3. Vascular bundle with one protoxylem (in red circle) (a), vascular bundle with two protoxylem (in red circle) (b), and individual isolated ring with remnant membranes (c).

The rings in protoxylem cell are associated with each other by a membrane, where the membrane is the original primary wall extensions before it gets ruptured during the growing phase (Liese 1998). The protoxylem lumen with individual isolated rings and remnant membranes (Fig. 3c) were observed in this study, but the tyloses were barely observed in the cells. Tyloses are often observed in protoxylem (developed from the surrounding parenchyma) of monopodial bamboo culms, which affect its conductance ability (Liese 1998; Ito et al. 2015).

Metaxylem Diameter and Phloem Diameter

The metaxylem comprises two large vessels, surrounded by one or two layers of sclerenchyma sheath (Fig. 4a, 4b). Metaxylem serves for water transport within culms and rhizomes, and its high conductivity is vital for foliage transpiration. The metaxylem diameter ranged from 78.3 to 150.6 µm. The structure of separating rim at the inner side of vessel, two distinct walled zonation (S1 and S2) (Fig. 4a, 4b), and the developed small branching lumens (Fig. 4c) inside the vessel lumen were observed. The observed vessels were axially oriented with branches for interconnection that formed vascular anastomoses (Fig. 4d). These observations corroborated a previous study on bamboo culm nodal zones (Ding and Liese 1997).

Fig. 4. Metaxylem surrounded by one or two layers of sclerenchyma sheath, separating rim at inner side of the metaxylem, and two distinct walled zonations (a), structure of inner side wall possess large simple perforation with numerous pit, two distinct walled zonations (S1 and S2) and perforation plate (b), small branching lumen developed to form the vascular anastomoses (c), and diagram of vascular anastomoses by Ding and Liese (1997) (d)

Figure 2f shows the transverse section of twist angle of small vascular bundles in the form of vascular anastomoses. This observation explains the unusual vascular bundle structure found in Phyllostachys pubescens rhizome by Ito et al. (2015), where the vascular bundles consist of two pairs of metaxylem. Table 2 shows that metaxylem diameter was significantly different (p < 0.01) with respect to study site, where the bigger metaxylem diameter was found at Kenaboi FR, followed by Amanjaya FR and Ayer Hitam FR (Table 3). The metaxylem diameter was not significantly different (p > 0.05) with rhizome age.

The phloem in the G. scortechinii rhizome consists of large, thin-walled sieve tubes and small companion cells, surrounded by fiber sheaths and sclerenchyma sheaths (Fig. 5a, 5b, and 5c). The companion cells were interconnected by sieve pores as explained by Liese (1998). Regardless of study site and rhizome age, the phloem diameter ranged from 86.4 to 193.3 µm. The phloem diameter was highly significantly different (p < 0.01) with study site, but not significantly different with rhizome age (Table 2). A significant difference (p < 0.05) but weak correlation (r = -0.241) was found between phloem diameter with study site. Correlation coefficient analysis also showed that there was no significant correlation between phloem diameter and rhizome age (Table 4).

Fig. 5. Phloem consists of large, thin-walled sieve tube, and small companion cells, surrounded by fiber strand (a), phloem consist of large, thin-walled sieve tube separated with metaxylem and protoxylem and sclerenchyma sheath (b), and inner side structure of phloem with smaller companion cell separated by thin wall (c).

Parenchyma and Lumen Diameter, and Cell Wall Thickness

The parenchyma in G. scortechinii rhizomes was vertically elongated with short cube-like ones, more rectangular in shape like the parenchyma in monopodial bamboo species (P. pubescens) (Tekpetey et al. 2010). The parenchyma varied in size, and it was connected with pits on all side walls (Fig. 6a, 6b, 6c, and 6d) rather than on only tangential wall as such found in bamboo culm internodes (Liese and Tang 2015).

Fig. 6. Parenchyma in new sprout (a), young rhizome (b), premature rhizome (c), and mature rhizome (d). The starch particle was also observed filling in some parenchyma cells (b, c, and d).

The parenchyma diameter ranged from 24.8 to 60.7 µm. Starch particles of the round or ellipsoidal types were observed in some parenchyma cells; they were more frequent in mature rhizomes, followed by premature and young rhizomes. No starch particles were observed in parenchyma cells in a new sprout (Fig. 6a, 6b, 6c, and 6d). The low frequency of starch particles is related to the period of sampling, as the starch content is higher in the dry season than in the rainy season (Abd-Latif 1996; Wahab et al. 2006). Magel et al. (2005) explained that the mobilization of starch occurs before a new shoot is sprouted to accommodate the growing season.

The parenchyma diameter was not significantly different with respect to study site, but it was significantly different (p < 0.01) with rhizome age and the interaction of study site and rhizome age. The results in Table 4 indicate an insignificant correlation (r = -0.065) between parenchyma diameter with study site. A moderate positive correlation (r = 0.400, p < 0.01) was found between parenchyma diameter with rhizome age. The range of parenchyma lumen diameter in this study was 22.62 to 57.70 µm.

Analysis of variance showed that parenchyma lumen diameter was not significantly different with study site, but significantly different (p < 0.01) with rhizome age and the interaction of study site and rhizome age (Table 2). The variation of parenchyma lumen diameter had no relationship with study site (r = -0.055). A significant (p < 0.01) moderate positive correlation (r = 0.350) was found between parenchyma lumen diameter with rhizome age. This result indicates that parenchyma lumen diameter increased with rhizome age.

Regardless of study site and rhizome age, the parenchyma cell wall thickness ranged from 0.46 to 2.62 µm. The parenchyma cell wall thickness was significantly different (p < 0.05) with study site, and it was highly significantly different (p < 0.01) with rhizome age and the interaction of study site and rhizome age (Table 2). Table 3 indicates that the oldest rhizome was highest in parenchyma cell wall thickness, followed by premature, young, and new sprout rhizome, at 1.78, 1.62, 1.40, and 0.92 µm, respectively, which is in agreement with previous work (Wahab et al. 2006; Liese and Tang 2015). The variation of parenchyma diameter, lumen diameter, and cell wall thickness shows that maturing occurs, such as thickening by deposition of additional lamella with consequent lignification.

However, these results contradicted a study by Hisham et al. (2006) on the same bamboo species (G. scortechinii) culms, where the parenchyma cell wall thicknesses were not significantly different with culms age. According to Table 4, parenchyma cell wall thickness has no significant correlation with study site, but had a strong positive correlation (r = 0.682, p < 0.01) with rhizome age. This result indicates that parenchyma cell wall thickness increased when rhizome age increased.

Fiber and Lumen Diameter, Cell Wall Thickness, and Length

The fiber was grouped in a fiber sheath in vascular bundles. The individual fiber is characterized by their slender-form, long and tapered ends; the fork end type was not observed in this study. Numerous pits were observed inside fiber lumen walls, as shown in Fig. 7a.

Fiber diameter ranged from 12.0 to 33.6 µm. The variation in fiber diameter was caused by the a) cell position in rhizome wall where the fiber near the epidermis as well as near rhizome lumen are thinner and possess one or more lamella less than in the middle wall, b) position within length of culms (Londono et al. 2002) (as well as in rhizome in this study), and c) their position in a vascular bundles such as direct contact with the surrounding parenchyma, protoxylem, and phloem (Liese and Weiner 1996). These effects can be observed in Fig. 1c and 7b.

Table 2 indicates that there were highly significant differences (p < 0.01) between fiber diameter with study site, rhizome age, and the interaction of study site and rhizome age. These results agreed with a study by Abd-Latif (1996) on bamboo culms, except on the interaction of both main effects. In contrast, Hisham et al. (2006) found that fiber diameter was found not significantly different with G. scortechinii culm age. The Pearson correlation analysis (Table 4) showed a moderate positive correlation (r = 0.376, p < 0.01) between fiber diameter with study site. The analysis also showed a moderate positive correlation (r = 0.367, p < 0.01) between fiber diameter with rhizome age. The positive correlation indicated that fiber diameter increased when rhizome age increased.

Regardless of study site and rhizome age, fiber lumen diameter ranged from 1.00 to 18.86 µm. The results in Table 2 indicate that fiber lumen diameter was not significantly different (p > 0.05) with study site, but was highly significantly different (p < 0.01) with rhizome age, and the interaction study site and rhizome age. Table 4 shows that there was no correlation between fiber lumen diameter with rhizome age (r = -0.095). These results suggested that the increasing rhizome age did not influence the variation of fiber lumen diameter, as indicated by a small F value (6.70) in Table 2. Similar findings were reported by Abd-Latif (1996) and Hisham et al. (2006).

Fig. 7. Pits cavity (in red circle) inside the fiber lumen wall (a), sizes of fiber lumen varies from inside to periphery in a vascular bundle (b). Fiber structure in new sprout (c), young rhizome (d), premature rhizome (e), and mature rhizome (f)

Furthermore, fiber cell wall thickness ranged from 2.07 to 9.96 µm. Regardless of rhizome age, fiber cell wall thickness was not significantly different with study site, but significantly different (p < 0.01) with rhizome age, which agreed with Abd-Latif (1996). The fiber cell wall thickness was significantly different (p < 0.05) with the interaction of study site and rhizome age (Table 2). Fiber cell wall thickness had no significant correlation with study site, as the Pearson correlation value was -0.153, but fiber cell wall thickness had a strong positive correlation with rhizome age (r = 0.634, p < 0.01). This result illustrates that fiber cell wall thickness increased with rhizome age.

Liese (1998) explained that the thickening of cell walls (regarding parenchyma and fiber) during development of their structure occurs due to the deposition of additional lamella layers but not due to the thickening of the existing cell walls. The anatomical changes during the development of fiber structure have been reported in other bamboo species (such as Fujii 1985; Alvin and Murphy 1988; Liese and Weiner 1996; Londono et al. 2002; Gan and Ding 2005).

A wide range of fiber length (339.0 to 2660.7 µm) was observed in G. scortechinii rhizomes (Fig. 8a, 8b). This could be due to the closed position or the unclear zonation between the internodes and nodes in rhizome walls. Liese and Tang (2015) reported that the fibers in culm nodes are shorter than in the internodes. Table 2 indicates that there were highly significant differences (p < 0.01) between fiber length with study site, rhizome age, and the interaction of study site and rhizome age. The correlation coefficient indicates a significant (p < 0.01) moderate positive correlation (r = 0.355) between fiber length with study site and with rhizome age, with r = 0.355 and 0.413, respectively. The positive correlation between fiber lengths with rhizome age illustrates that the fiber length increased with increasing rhizome age.

Fig. 8. Long (a), medium, and short slender fiber (b) with both tapered end

Hydraulic Conductance

The hydraulic conductance of rhizomes ranged from 1.289 to 5.333 m² s^–¹ MPa^–¹. Table 2 shows that the hydraulic conductance was highly significantly different (p < 0.01) with study site, rhizome age, and their interaction. Higher hydraulic conductance was found in Ayer Hitam FR, followed by in Kenaboi FR and Amanjaya FR, with values of 3.797, 3.390 and 3.073 m²·s^–¹ MPa^–¹, respectively. The new sprout rhizome demonstrated the highest hydraulic conductance (4.795 m² s^–¹ MPa^–¹), followed by the young (3.680 m² s^–¹ MPa^–¹), pre-mature (3.065 m² s^–¹ MPa^–¹), and mature rhizome (2.140 m² s^–¹ MPa^–¹).

There was no significant correlation (r = 0.283) between hydraulic conductance with study site, but there was a significant correlation (r = -0.918) with rhizome age (Table 4). The negative correlation indicates that hydraulic conductance decreased with age. Higher hydraulic conductance in younger versus older rhizomes illustrates that the hydraulic resistance increased up to an average of 23% at each increment of age. During the late phase of culms elongation, fiber cell walls in the phloem cap are actively thickening and almost reach their full secondary cell wall deposition during the first growing season. This thickening results in multilayered cell walls that begin around the edge of conducting elements (phloem and metaxylem), and continuously thicken towards the outer part of a vascular bundles (Bhat 2003; Gritsch et al. 2004).

Like other bamboo species, G. scortechinii is unable to grow new conductance elements and, hence, may show vulnerability to metaxylem dysfunction due to cavitation (Johnson et al. 2009; Marine 2009) and metaxylem implosion (Cochard et al. 2004), which lead to loss of hydraulic conductivity (Tyree and Zimmerman 2002). The growing organs develop to mature phase with continuous changes in density, strength properties, and chemical constituents (Liese 1998; Hisham et al. 2012; Xu et al. 2014; Wang et al. 2016).

Relationship of Anatomical Characteristics with Hydraulic Conductance

The results in Table 4 indicate that only parenchyma diameter and parenchyma lumen diameter had a significant (p < 0.01) relationship (r = -0.470 and -0.466, respectively) with hydraulic conductance. The negative relationship of parenchyma diameter and parenchyma lumen diameter with hydraulic conductance illustrates that hydraulic conductance decreases with increasing parenchyma diameter and parenchyma lumen diameter. However, the sizes of parenchyma diameter and lumen diameter do not imply a direct determinant factor of hydraulic conductance unless the parenchyma cell wall thickness also showed a significant relationship with hydraulic conductance. This is because the size of parenchyma diameter and lumen diameter varied with the location such as near vascular bundles or the distance from periphery of rhizome.

The results show that parenchyma cell wall thickness did not have a significant relationship (r = -0.325) with hydraulic conductance. The parenchyma cell wall thickness showed a weak negative relationship with hydraulic conductance, where the p-value of the correlation coefficient was nearly significant (0.053).

The conductance elements such as protoxylem, xylem, and phloem diameter did not have a significant relationship (r = 0.022, 0.064, and 0.154, respectively) with hydraulic conductance. This study did not measure the conductance elements cell wall thicknesses, which are more likely to determine the relationship with hydraulic conductance due to the irregular or uneven thickness of cell wall membranes (Figs. 3, 4, and 5). Furthermore, chemical substances such as ash content, cellulose, lignin, and extractives show a significant relationship with anatomical changes during the maturation of bamboo culms (Abd-Latif 1996; Hisham et al. 2006; Li et al. 2007; Wang et al. 2016; Mohamed et al. 2019). The senescent effect has consequences during the natural dying of culms. This effect includes blocking off water conductance in metaxylem by tylosses and slime substances, and the phloem callose occlusions that decrease the functional efficiency (Liese and Weiner 1996; Liese and Tang 2015).

In the present study, the accumulated substances could be lost during the boiling process of sample preparation. Furthermore, the differences between living and dead cells or substances that accumulate were hard to determine using the sputter coater method. It can be measured or viewed by staining with 1% potassium permanganate prepared in citrate buffer (Cho et al. 2008) or with 1% safranin-O and counter-stained with 1% aqueous Alcian Blue (Wang et al. 2016). Cho et al. (2008) stained samples with 0.0001% acrifl avine to obtain confocal images for lignin fluorescence.

The hardness of rhizome samples directed the choice of sample preparation method in this study. Rao (1985) reported the differences between soft tissues in bamboo shoot and hard tissues in mature bamboo culms and also between the nodes and internodes. Liese and Weiner (1996) used different approaches to obtain smooth surfaces between soft and extremely hard samples of 12 different ages of Phyllostachys viridiglaucescens culms. Therefore, further studies on chemical substances in relation to hydraulic conductance could improve the understanding regarding relationship with age and hydraulic conductance.

CONCLUSIONS

All measured anatomical characteristics were found significantly different with study site except for parenchyma diameter, parenchyma lumen diameter, and fiber cell wall thickness.
Vascular bundle diameter, parenchyma diameter, parenchyma lumen diameter, parenchyma cell wall thickness, fiber diameter, fiber wall thickness, and fiber length increased with increasing rhizome age, while radial to tangential ratio, protoxylem diameter, and fiber lumen diameter decreased with increasing rhizome age.
The hydraulic conductance was significantly different with study site and rhizome age. The negative correlation indicated that the hydraulic conductance decreased with increasing rhizome age.
All measured characteristics including the conductance element had an insignificant relationship with hydraulic conductance, except the parenchyma diameter and lumen diameter.

ACKNOWLEDGMENTS

The authors are grateful to the Forestry Department Peninsular Malaysia for the cooperation and permission to conduct this study at Amanjaya Forest Reserve, Perak and Compartment 189, Kenaboi Forest Reserve, Negeri Sembilan.

REFERENCES CITED

Abd-Latif, M. (1996). Some Selected Properties of Two Malaysian Bamboo Species in Relation to Age, Height, Site and Seasonal Variation, Ph.D. Dissertation, Universiti Putra Malaysia, Serdang, Malaysia.

Alvin, K. L., and Murphy, R. J. (1988). “Variation in fibre and parenchyma wall thickness in culms of the bamboo Sinobambusa tootsik,” International Association of Wood Anatomist Journal 9(4), 353-361. DOI: 10.1163/22941932-90001095

Azmy, H. M., Norini, H., and Razali, W. W. M. (1997). Management Guidelines and Economic of Natural Bamboo Stands, Forest Research Institute Malaysia, Kepong, Malaysia.

Banik, R. L. (1993). “Morphological characters for culm age determination of different bamboos of Bangladesh,” Bangladesh Journal of Forest Science 22, 18-22.

Banik, R. L., and Islam, S. A. M. N. (2005). “Leaf dynamics and above ground biomass growth in Dendrocalamus longispathus Kurz,” Journal of Bamboo and Rattan 4(2), 143-150. DOI: 10.1163/1569159054699335

Bhat, K. V. (2003). “Anatomical changes during culm maturation in Bambusa bambos (L.) Voss and Dendrocalamus strictus Nees,” Journal of Bamboo and Rattan 2(2), 153-166.

Cho, H, C., Lee, K. H., Kim, J. S., and Kim, Y. S. (2008). “Micromorphological characteristics of bamboo (Phyllostachys pubescens) fibers degraded by a brown rot fungus (Gloeophyllum trabeum),” Journal of Wood Science 54, 261-265. DOI: 10.1007/S10086-007-0937-1

Cochard, H., Froux, F., Mayr, S., and Coutard, C. (2004). “Xylem wall collapse in water-stressed pine needles,” Plant Physiology 134, 401-408. DOI: 10.1104/pp.103.028357

Ding, Y. L., and Liese, W. (1997). “Anatomical investigations on the nodes of bamboo,” in: The Bamboos, L. Soc and G. Chapman (eds.), Academic Press, London.

Ding, Y. L., Tang, G. G., and Chao, C. S. (1997). “Anatomical studies on the culm neck of some pachymorph bamboos,” in: The Bamboos, L. Soc and G. Chapman (eds.), Academic Press, London.

Do, F., and Rocheteau, A. (2002). “Influence of natural temperature gradients on measurements of xylem sap flow with thermal dissipation probes. 2. Advantages and calibration of a noncontinuous heating system,” Tree Physiology 22(9), 649-654. DOI: 10.1093/treephys/22.9.649

Fujii, T. (1985). “Cell-wall structure of the culm of Azumanezasa (Pleioblastus chino Max.),” Mokuzai Gakkaishi 31, 865-872.

Gan, X. H., and Ding, Y. L. (2005). Developmental anatomy of the fiber in Phyllostachys edulis culm,” The Journal of the American Bamboo Society 19(1), 16-22.

Gritsch, C. S., Kleist, G., and Murphy, R. J. (2004). “Developmental changes in cell wall structure of phloem fibres of the bamboo Dendrocalamus asper,” Annals of Botany 94, 497-505. DOI: 10.1093/aob/mch169

Hisham, H. N., Othman, S., Rokiah, H., Abd-Latif, M., and Tamizi, M. M. (2006). “Characterization of bamboo Gigantochloa scortechinii at different ages,” Journal of Tropical Forest Science 18(4), 236-242.

Hisham, H.N., Othman, S., Azmy, M., and Norasikin, A. L. (2012). “The decay resistance and hyphae penetration of bamboo Gigantochloa scortechinii decayed by white and brown rot fungi,” International Journal of Forestry Research, Article ID 572903. DOI: 10.1155/2012/572903

Ito, R., Miyafuji, H., and Kasuya, N. (2015). “Rhizome and root anatomy of Moso bamboo (Phyllostachys pubescens) observed with scanning electron microscopy,” Journal of Wood Science 61,431-437. DOI: 10.1007/S10086-015-1482-Y

Johnson, D. M., Meinzer, F. C., Woodruff, D. R., and McCulloh, K. A. (2009). “Leaf xylem embolism detected acoustically and by cryo-SEM, corresponds to decreases in leaf hydraulic conductance in four evergreen species,” Plant, Cell, and Environment 32, 828-836. DOI: 10.1111/J.1365-3040.2009.01961.X

Li, R., Werger, M. J. A., During, H. J., and Zhong, Z. C. (1998). “Carbon and nutrient dynamics in relation to growth rhythm in the giant bamboo Phyllostachys pubescens,” Plant and Soil 201(1), 113-123. DOI: 10.1023/A:1004322812651

Li, X. B., Shupe, T. F., Peter, F. G., Hse, C. Y., and Eberhardt, T. L. (2007). “Chemical changes with maturation of the bamboo species Phyllostachys pubescens,” Journal of Tropical Forest Science 19(1), 6-12.

Liese, W. (1987). “Anatomy and properties of bamboo,” in: Recent Research on Bamboos, A. N. Rao, G. Dhanarajan, and C. B. Sastry (eds.), Chinese Academy of Forestry, Beijing.

Liese, W. (1998). The Anatomy of Bamboo Culms (Technical Report No. 18), International Network for Bamboo and Rattan, Beijing.

Liese, W., and Tang, T. K. H. (2015). “Properties of the bamboo culm,” in: Tropical Forestry: Bamboo: The Plant and its Uses, W. Liese, and M. Kohl (eds.), Springer, Hamburg, Germany.

Liese, W., and Weiner, G. (1996). “Ageing of bamboo culms. A review,” Wood Science and Technology 30(2), 77-89. DOI: 10.1007/BF00224958

Londona, X. (1992). “Growth development of Guadua angustifolia: A case study in Colombia,” in: Bamboo and Its Use. Proceeding of International Seminar on Industrial Use of Bamboo,” International Association of Wood Anatomist Bulletin 13, 403-410.

Londono, L., Camayo, G. C., Riano, N. M., and Lopez, Y. (2002). “Characterization of the anatomy of Guadua angustifolia (Poaceae: Bambusoideae) culms,” The Journal of the American Bamboo Society 16(1), 18-31.

Magel, E., Kruse, S., Lu¨the, G., and Liese, W. (2005). “Soluble carbohydrates and acid invertases involved in the rapid growth of developing culms in Sasa palmata (Bean) Camus,” Bamboo Science Culture 19, 23-29.

Marine, Z. (2009). Sap flow dynamics of a tropical, woody bamboo: deductions of physiology and hydraulics within Guadua angustifolia, Unpublished dissertation submitted in partial fulfillment of the requirements for senior honors. Washington University, St. Louis, MO, USA.

Mohamed, J., Hamid, H. A., Nuruddin, A. A., and Majid, N. M. N. A. (2019). “Chemical attributes of Gigantochloa scortechinii bamboo rhizome in relation with hydraulic conductance,” BioResources 14(4), 8155-8173. DOI: 10.15376/biores.14.4.8155-8173

Philips Electron Optics (PEO) (1996). Environmental Scanning Electron Microscopy: An Introduction to ESEM®, Eindhoven, Netherlands.

Rao, A. N. (1985). “Structure and properties: Anatomical studies on certain bamboos growing in Singapore,” in: Recent Research on Bamboos, A. N. Rao, G. Dhanarajan, and C. B. Sastry (eds.), Chinese Academy of Forestry, Beijing.

Rodrigues, F. A., Vale, F. X. R., Datnoff, L. E., Prabhu, A. S., and Korndorfer, G. H. (2003). “Effect of rice growth stages and silicon on sheath blight development,” Phytopathology 93(3), 256-61. DOI: 10.1094/phyto.2003.93.3.256

Schweingruber, F. H. (2007). Wood Structure and Environment, Springer-Verlag, Heidelberg.

Tekpetey, S. L., Mensah, N. K. F., and Acheampong, A. (2010). “Bamboo in green construction in ghana: The studies of selected anatomical properties,” in: International Convention of Society of Wood Science and Technology and United Nations Economic Commission for Europe – Timber Committee, Geneva, Switzerland.

Tsuda, M., and Tyree, M. T. (1997). “Whole-plant hydraulic resistance and vulnerability segmentation in Acer saccharinum,” Tree Physiology 17, 351-357. DOI: 10.1093/treephys/17.6.351

Tsuda, M., and Tyree, M. T. (2000). “Plant hydraulic conductance measured by the high pressure flow meter in crop plants,” Journal of Experimental Botany 51(345), 823-828. DOI: 10.1093/JEXBOT/51.345.823

Tyree, M. T., and Zimmermann M. H. (2002). Xylem Structure and the Ascent of Sap, (2^nd Ed.), Springer, New York, NY.

Tyree, M. T., Yang, S., Cruiziat, P., and Sinclair, B. (1994). “Novel methods of measuring hydraulic conductivity of tree root systems and interpretation using AMAJZED: A maize-root dynamic model for water and solute transport,” Plant Physiology 104, 189-99.

Tyree, M. T., Sandra, P., John, B., and John, A. (1995). “Dynamic measurements of root hydraulic conductance using a high-pressure flow meter in the laboratory and field,” Journal of Experimental Botany 46(1), 83-94. DOI: 10.1093/JXB/46.1.83

Wahab, R., Mohamed, A., Samsi, H. W., Yunus, A. A. M., and Moktar, J. (2006). “Physical characteristics, anatomy and properties of managed Gigantochloa scortechinii natural bamboo stands,” Journal of Plant Sciences 1(2), 144-153. DOI: 10.3923/jps.2006.144.153

Wang, Y., Zhan, H., Ding, Y., Wang, S., and Lin, S. (2016). “Variability of anatomical and chemical properties with age and height in Dendrocalamus brandisii,” BioResources 11(1), 1202-1213. DOI: 10.15376/biores.11.1.1202-1213

Xu, B., Liu, S., and Zhu, T. (2014). “Comparison of variations in the chemical constituents of the rhizome and culm of Phyllostachys pubescens at different ages,” BioResources 9(4), 6745-6755. DOI: 10.15376/biores.9.4.6745-6755

Yoshizawa, N., Satoh, I., Yokota, S., and Idei, T. (1991). “Lignification and peroxidase activity in bamboo shoots (Phyllostachys edulis A. et C. Riv.),” Holzforschung 45(3), 169-174.

Zhang, Z., Hu, C., and Jin, A. (1996). “Observation of the morphology and the structure of Phyllostachys praecox rhizome lateral bud developing into shoot,” Journal of Bamboo Research 15(2), 60-66.

Article submitted: May 23, 2019; Peer review completed: September 23, 2019; Revised version received: September 24, 2019; Accepted: September 26, 2019; Published: September 30, 2019.

DOI: 10.15376/biores.14.4.9082-9099