DECAY RESISTANCE OF BAMBOO (GIGANTOCHLOA SCORTECHINII) COMPARED TO 24 MALAYSIAN HARDWOOD

Author
Norul Hisham Hamid & Abd. Latif Mohmod & Othman Sulaiman ¹

Introduction

Bamboos, like other lignocelluloses materials are subject to biodegradation by fungi and insects under particular condition and may affected their quality during the processing activities. Liese (1985) stated that bamboo is attacked by both fungi and insects above the fiber saturation point by brown rot, white rot and soft rot. The bamboo service life is estimated only from 6 month to 3 years when in soil contact (Liese 1985 and George 1985). 
In Malaysia, bamboo is amongst alternative resources to support the local wood industries need. Gigantochloa scortechinii which broadly found in Peninsular Malaysia is focused to explore their potential uses. Details anatomical, physical and mechanical properties are intensively studied by Abd. Latif & Mohd. Tamizi (1992), Abd. Latif & Mohd. Zin (1992), Abd. Latif & Liese (1998) and Abd. Latif & Pham (2001). Nevertheless, information regarding their decay resistance in comparing to Malaysian hardwood is not systematically known. Understanding their decay resistance class will help in proper management in industrial application.

Material and Methods

Source of materials

Gigantochloa scortechinii with three different age classes namely 0.5, 1.5, 3.5, 5.5 and 6.5 years old grown in natural stand Nami, Kedah (northern part of Peninsular Malaysia) were chosen. Age of the culms was recognized from the first day of their emerging period. Those culms were taken within the same clump. They were harvested and immediately coated with paint and kept inside the ice box before being transferred to the laboratory.

Preparation of the specimens

The middle portion of the internodes sixth was selected. They were then cut into ring size of 3 cm height and trimmed into size of 1 cm width. The specimens were then oven dried to 103±2 ⁰ C in 24 hours and finally was measured into two decimal places. Details basic characteristic of the culms is shown in Table 1.

Table 1. Basic characteristics of samples.

Basic characteristics	0.5 years	3.5 years	6.5 years
Internodes length (cm)	32.9	35.2	40
Internodes diameter (cm)	14.7	10.5	16
Culms wall thickness (mm)	8	7	7

Exposure to fungi 

The specimens were oven dried weight at 103±2 ⁰ C, weight and sterilized with propylene oxide in two days prior to exposure to culture of the white rot Coriolus versicolar (L.ex Fr.) and brown rot Coniophora puteana (Scum. Ex Fr.) growing on agar media in Petri dishes. A 4 % malt extract and 2 % agar technical medium was used for the two basidiomycetes with incubation at 22 ⁰ C for eight weeks. 

Determination of deterioration

After exposure time, the adhering mycelium was cleaned softly with brush, weighed and then dried to determine loss in dry weight by comparison with the pre-exposure value. Due to variation in density between the culms age, the scope of decay was expressed both as total weight loss material decayed by fungi and the more common used percent weight loss. Mean value of density and lignin content measured by weight displacement method and Tappi T-13m-54 (Anon 1978) are given in Table 2.

Table 2. Mean value of density and lignin content.

Age (years)	Density (g/cm 3 )	Lignin (%)
0.5	0.53	23.4
3.5	0.61	26.8
6.5	0.68	28.7

Result and Discussions

The total weight loss and percentage weight loss of different culms age and decay fungi are given in Table 3. All age classes were clearly less resistance to brown rot decay than white rot. The percent weight loss of Gigantochloa scortechinii exposed to brown rot is between 5.30 to 9.90 % compared 8.90 to 9.95 % from white rot respectively. This finding is in good accord with the observation by Liese (1985). The trend probably due to white rot has capability to utilize both carbohydrate and lignin, while brown rot only modifies the lignin during the process (Erickson 1978).

Table 3. Decay after 8 weeks exposure

Age (years)	TWC (mg)		PWL (%)
	White rot	Brown rot	White rot	Brown rot
0.5	140	150	9.90	9.95
3.5	120	130	9.24	9.49
6.5	60	90	5.30	8.90

TWC- total weight loss, PWL-percentage weight loss

Regarding the maturation, the resistance of bamboo is related to the culm age. Generally, culm aged 6.5 years is the most resistance against followed by 3.5 years and 0.5 years as greater degree of lignification is probably the major factor reduced susceptibility of fungi. Younger culms (0.5 years) more susceptibility to fungi probably is due to incomplete lignification process of fibers and part of the ground tissue parenchyma (Murphy et. al. 1996). 
Relative to the 24 Malaysian hardwoods, Gigantochloa scortechinii was intermediate in its resistance to White rot fungus between heavy hardwood and medium hardwood (Table 4). In details, the decay resistance of 6.5 years old culm was equivalent to Kapor (Dryobalanops aromantica), while 0.5 and 3.5 years old culm was in between Kempas (Koompasia malaccensis) and Keruing (Dipterocarpus sp.). Greater microfibrillar layered in bamboo cell walls and fasten maturation stage probably is the reason their resistance in comparing to some Malaysia hardwood.

Table 4. Percent weight loss after exposure to White rots fungi of Malaysian hardwood.

Number	Trade Name	Scientific name	Weight loss (%)
1	Balau	Shorea sp.	1.2
2	Chengal	Neobalanocarpus heimii	1.4
3	Giam	Hopea sp.	1.7
4	Keranji	Dialium sp.	0.3
5	Merbau	Intsia palembanica	3.8
6	Resak	Vatica sp.	0.3
7	Kapor	Dryobalanops aromantica	5.3
8	Kempas	Koompasia malaccensis	8.7
9	Keruing	Dipterocarpus sp.	15.3
10	Mata ulat	Kakoona sp.	17.7
11	Punah	Tetramerista glabra	21.4
12	Rengas	Anacardeaceae	0.0
13	Bintangor	Colaphyllum sp.	18.5
14	Durian	Durio sp.	19.5
15	Jelutong	Dyera cosculata	31.6
16	Meranti bakau	Shorea rugosa	11.1
17	Meranti, dark red	Shorea sp.	14.5
18	Meranti, white	Shorea sp.	36.1
19	Meranti, yellow	Shorea sp.	30.5
20	Merawan	Shorea sp.	1.8
21	Mersawa	Anisoptera sp.	14.6
22	Perupok	Lophopetalum sp.	47.7
23	Ramin	Gonystylus sp.	35.8
24	Rubberwood	Hevea brasiliensis	36.9

Note: Numbers 1-6 is heavy hardwood, 7-12 is medium hardwood, and 13-24 is light Hardwood. (Sources: Yamamoto & Hong, 1989).

Conclusion

This study indicates that G. scortechinii has less susceptibility against brown rot compared to white rot fungi. The degree of resistance is greatly influenced by the culm age and lignin content. In comparing to the 24 Malaysia hardwoods, Gigantochloa scortechinii was intermediate between heavy hardwood and medium hardwood.

References

Abd. Latif, M. & Mohd Tamizi, M. 1992. Variation of anatomical properties of three Malaysia bamboos from natural stand. Journal of Tropical Forest Sciences 5(1):90-96.
Abd. Latif, M. & Mohd. Zin, J. 1992. Trends of variation in some physical properties of Gigantochloa scortechinii. INBAR Information Centre, India Bulletin 2(2): 7-12.
Abd. Latif, M. & Liese, W. 1998. Influences of age, culm, height, site and harvesting month on moisture content level of two Malaysian bamboos. Paper presented at the VI International Bamboo Workshop and V International Bamboo Conferences. 2-6 November 1998. San Jose, Costa Rica.
Anonymous. 1978. TAPPI Official Testing Procedure. Technical Association of the Pulp and Paper Industry, Atlanta. 220p.
Erickson, K.E. 1978. Enzyme mechanism involved in cellulose hydrolysis by the white rot fungus, Sporatichum pulverulentum. Biotechnology Bioengeneering 20: 317-332.
George, J. 1985. Preservative treatment of bamboo. Pp 233-247 in W.K.P. Findley (ed.) Preservative in the Tropics, Dordrecht: Martinus Nijhoff/Dr W. Junk.
Liese, W. 1985. Bamboos-Biology, Silvics, Properties, Utilization. Schriftenreihe der GTZ No. 180.
Murphy, R.J., Othman, S. & Alvin, K.L. 1996. Ultrastructure aspects of cell wa


For further details log on website :
http://www.fao.org/docrep/article/wfc/XII/0039-b4.htm