Gigantochloa pseudoarundinacea

Gigantochloa pseudoarundinacea (Steudel) Widjaja

Reinwardtia 10(3): 305 (1987).
2n = 72 (hexaploid)

Origin and geographic distribution
The origin of G. pseudoarundinacea is not known; it is only found in cultivation. It is widely cultivated in Indonesia (Java, Bali, Sumatra, Mentawai Islands) and has been introduced to Peninsular Malaysia and India. For map click: Map368.TIF.

In Indonesia G. pseudoarundinacea is used for building material, water pipes, furniture, household utensils, chopsticks and toothpicks. It is also used to make basketry (although G. apus (J.A. and J.H. Schultes) Kurz is preferred) and musical instruments (although G. atroviolacea Widjaja is preferred). The young shoots are eaten as a vegetable, especially those of less robust forms. The culms might be used to make charcoal.

Production and international trade
In Indonesia, G. pseudoarundinacea is the second in importance after G. apus and plays a prominent role in the rural economy. Local production and trade of culms and derived products are considerable, but no statistics are available.

The fibre dimensions for culms of G. pseudoarundinacea are: length 2.75-3.27 mm, diameter 24.55-37.97 µm; the number of fibres increases by about 10% from the bottom to the top of the culm. Specific gravity is 0.5-0.7 (internodes) and 0.6-0.8 (parts with nodes). The modulus of elasticity is 19,440-28,594 N/mm2, the modulus of rupture 171-207 N/mm2, the tensile strength 128-192 N/mm2. The energy value for charcoal of culms of G. pseudoarundinacea is about 30,000 kJ/kg.
In Indonesia (West Java) G. pseudoarundinacea culms grown on hill slopes (500 m altitude, 4200 mm annual rainfall) are stronger (higher specific gravity, bending and tensile strength) than culms grown in valleys.

A densely tufted, sympodial bamboo, with the centre of the clump irregularly raised above the ground. Culm 7-30 m tall, 5-13 cm in diameter, wall up to 2 cm thick; internodes up to 40-45(-60) cm long, green to yellow-green, yellow striped, initially with scattered appressed brown hairs on the upper parts, glabrous and smooth when older; lower nodes with verticillate aerial roots. Branches arising from all nodes above 2-3 m from the ground with one dominant branch at each node. Culm sheath truncate, 35 cm long or longer, deciduous, when young, dark green and papery at the margin and brown hairy becoming glabrous with age; blade ovate-oblong, acute at the apex, about as long as the sheath, hirsute at base, spreading to reflexed; ligule up to 5 mm long, dentate, fine hairy at top; auricles up to 4 mm tall and 17 mm long in lateral extent, with a variable low and wavy rim, when young with up to 5 mm long bristles. Young shoots yellow-green, flushed with orange on the sheath apices and green striped, with appressed, acute, brown to golden-brown hairs. Leaf blade lanceolate, 22-25 cm x 2.5-5 cm, glabrous or finely hairy at lower surface; lower sheaths with slightly emarginate collar-like callus; ligule up to 2 mm long, irregularly toothed with fine hairs; auricles firm, raised at the end up to 1 mm and joined to the ligule. Inflorescences appearing on leafless culms, up to 75 cm long, with clustered pseudospikelet groups 1-9 cm apart and up to 148 pseudospikelets in a cluster; spikelet ovoid, subacute, 7.5-10 mm long, with 4 perfect and 1 sterile florets. Caryopsis unknown.

Growth and development
One year after planting of a cutting, 7-10 culms have emerged. Per year about 8-9 culms per clump reach full size. A young culm grows fast, attaining full height in 3-4 months with an average growing rate of 3.4 cm per day.
Flowering occurs when the clump is 50-60 years old; it flowers gregariously, after which the clump dies.

Other botanical information
G. pseudoarundinacea, G. atter (Hassk.) Kurz, G. atroviolacea Widjaja and G. robusta Kurz, were formerly united into one complex species G. verticillata. They can easily be distinguished from each other. G. atroviolacea has purplish to violet culms while G. pseudoarundinacea has yellow striped yellowish-green ones. The culm sheath auricles of G. pseudoarundinacea are up to 17 mm long and up to 4 mm tall with a wavy rim; in G. atter they are rounded and slightly curved outward, 6-9 mm long and 3-7 mm tall; in G. robusta they are well-developed along the sheath apex, crisped and joined to the blade's base, up to 7 mm tall with long bristles; in G. atroviolacea they are rounded, 5-8 mm wide and 4-8 mm tall.
G. pseudoarundinacea is quite variable in West Java, where people distinguish 3 forms: (1) 'awi andong': the most robust form, with walls 1.5-2 cm thick, mostly green with few yellow stripes, most frequently used for construction; often some internodes are not closed by partitions so that the central cavity runs without interruption for some length (useful for water pipes and containers); (2) 'awi andong leah': a less robust form with walls up to 1 cm thick and rather short lower internodes with prominent nodes, more prominently yellow striped; this form is preferred for its tasty young shoots; (3) 'awi andong keukeus': the smallest form, mostly used for its edible young shoots.
In Central and East Java G. pseudoarundinacea is apparently uniform because only one kind is known, called 'pring surat'.

G. pseudoarundinacea is grown in the perhumid tropics from sea-level up to about 1200 m altitude, in areas with an annual rainfall of 2350-4200 mm, average temperature of 20-32ºC and average relative humidity of over 70%. It occurs on sandy loams and alluvial soils.

Propagation and planting
G. pseudoarundinacea is only propagated vegetatively by rhizome, culm or branch cuttings. Cuttings from flowering clumps should be avoided because they will start flowering soon after planting. Culm cuttings have shown a survival rate of nearly 100%. In Indonesia, the best time for planting is in the rainy season from December to March. Recommended spacing is 8 m x 8 m, and high rainfall areas are preferred.

Weeding, watering and loosening of the soil are important until the clumps are well-established. Organic and chemical fertilizers are applied for high production, but no recommended amounts are known. Cleaning the clumps from culm remnants and earthing up stimulate the growth of new culms.

Diseases and pests
G. pseudoarundinacea is usually attacked by a witches' broom (Epichloe bambusae) but this disease has no harmful effect on culm production. The most serious pest causing much damage is Dinoderus minutus, a borer attacking harvested culms.

First harvesting may start 3 years after planting, preferably in the dry season (April-October in Java). It is recommended to harvest only 3-year-old culms and to cut just above the ground. To promote regeneration, it is recommended to earth up and to mulch the base of the harvested culms. For East Java, a half clear-felling system in a cycle of 3 years is recommended.

The annual yield of mature culms from a plantation with 275 clumps per ha (6 m x 6 m) is estimated at 1650 per ha or about 6 culms per clump. If converted to charcoal, about 18% good charcoal and 4% brand and broken charcoal are produced.

Handling after harvest
Traditionally, culms are left leaning upright against a tree for some days before being used. Sometimes culms are first soaked in running water or mud for some time. Experiments with preservation by soaking in a chemical solution of e.g. caustic soda or boric acid show promising results.

Genetic resources and breeding
In Indonesia small germplasm collections exist in Bogor (experimental gardens of the Forest Research and Development Centre, Arboretum of the Agricultural University (IPB) and the Perhutani Bamboo Germplasm Garden) and in Lampung (Sumatra). Conservation of existing variation is needed. There are no breeding programmes; in the germplasm collection at Lampung natural hybrids of G. pseudoarundinacea produced viable seed.

The prospects for G. pseudoarundinacea are promising. It produces valuable construction material and its culms also appear to be suitable for the chopstick industry. Although research is needed on large-scale cultivation techniques, priority should be given to obtaining cultivars resistant to post-harvest pests.

E.A. Widjaja

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