Gigantochloa apus

Gigantochloa apus (J.A. and J.H. Schultes) Kurz

Nat. Tijdschr. Ned. Ind. 27: 226 (1864).
2n = 72 (hexaploid)

Origin and geographic distribution
G. apus is probably native to Burma (Myanmar) (Tenasserim) and southern Thailand. It was possibly introduced to Java during prehistoric human migrations. In Java it is now widely cultivated, but wild or naturalized populations of G. apus also occur on Mount Salak (West Java) and in Blambangan (East Java). In Indonesia it has spread to South Sumatra, Central Sulawesi and Central Kalimantan. For map click: Map517.TIF. Occasionally it is cultivated in experimental or botanical gardens in the tropics.

G. apus is very important in the Indonesian rural economy because it is much used for making cooking utensils, fishery utensils, furniture, ropes or strings, and in basketry.
Its culms are durable and used as building material for roofings, walls, scaffoldings and bridges. Culms can be split into fine strips for weaving hats, baskets and other objects; when split fine and the pieces bent, the surface does not chip off. In the absence of more suitable species, G. apus is sometimes used to make musical instruments, although the quality of the tones produced is inferior. G. apus is unsuitable for making chopsticks or toothpicks mechanically, because it has overlapping fibres.
Young shoots are very bitter. In Java the freshly cut shoots are burried in mud for 3-4 days to remove the bitter taste, before they are consumed as a vegetable.

Production and international trade
G. apus is the most important bamboo of Indonesia, but no production figures are available. It is traded mainly locally, e.g. to handicraft producers.

The fibre dimensions in the culm of G. apus are: length 0.9-5.5 mm, diameter 5-36 µm, wall thickness 1-3 µm. At an average moisture content of 54.3% (green culms) and 15.1% (air-dried culms) the mechanical properties of 3-year-old culms are respectively: modulus of rupture 102.0 N/mm2 (green, with nodes), 71.5 N/mm2 (green, without nodes), 87.5 N/mm2 (air dried, with nodes), 74.9 N/mm2 (air dried, without nodes); compression strength parallel to grain 24.0 N/mm2 (green, with nodes), 23.5 N/mm2 (green, without nodes), 37.5 N/mm2 (air dried, with nodes), 33.9 N/mm2 (air dried, without nodes); shear strength 7.68 N/mm2 (green, with nodes), 5.99 N/mm2 (green, without nodes), 7.47 N/mm2 (air dried, with nodes), 7.65 N/mm2 (air dried, without nodes); tensile strength 294 N/mm2 (green), 299 N/mm2 (air dried).
The approximate chemical composition of the culm is: holocellulose 52.1-54.7%, pentosans 19.1-19.3%, lignin 24.8-25.8%, ash 2.7-2.9%, silica 1.8-5.2%; the solubility in cold water is 5.2%, in hot water 5.4-6.4%, in alcohol-benzene 1.4-3.2% and in 1% NaOH 21.2-25.1%. Starch content fluctuates between 0.24-0.71%, depending on the season. The nodes often contain a dull bluish-white deposit of silicic acid.

Open tufted, sympodial bamboo. Culm erect, 8-30 m tall, 4-13 cm in diameter, wall up to 1.5 cm thick, greyish-green to bright or yellowish green, glabrous, shiny, covered with white wax when young; internodes 20-60(-75) cm long; nodes slightly swollen on the outside. Branches arising from the upper half only. Culm sheath narrowly trapezoid, 7-35 cm x 8-26 cm, persistent, green and covered with dark brown hairs when young, turning yellow-brown and glabrous at maturity; blade ovate-triangular, 3-10(-18) cm x 2-5 cm, spreading to deflexed when the culm elongates, ultimately deciduous, on adaxial side covered with deciduous dark brown, appressed hairs; ligule 2-4 mm long, irregularly toothed; auricles 4-8 mm wide, 1-3 mm long, firm, tallest at the outer ends, with slender bristles on the edges. Young shoots slender, with appressed blackish brown hairs, light green to grey-green, the blades spreading to deflexed, tinged yellowish. Leaf blade lanceolate, 13-49 cm x 2-9 cm, slightly hairy beneath when young; sheath dark brown hairy along the margin; ligule 2-4 mm long, finely hairy at the edge; auricles 1-2 mm long, rounded, firm, glabrous. Inflorescences borne on leafy branches bearing groups of pseudospikelets 1-8.5 cm apart, each group with up to 30 pseudospikelets; spikelet narrowly ovate, 13-22 mm x 2-3 mm, slender, with 2-3 empty glumes and 3 perfect florets. Caryopsis up to 12 mm x 2 mm, glabrous, longitudinally furrowed on one side.

Growth and development
One year after planting the vegetatively obtained propagules, about 10-15 culms will emerge; they are harvestable 1-3 years later, depending on the use. A young culm grows to its full height before starting to produce branches. Branching is initiated at about 8-11 nodes from the top and is followed by branching from the next two nodes down. Then development continues both upward and downward along the culm until branches are produced at all nodes in upper half of the culm. G. apus flowers very rarely. In Indonesia, flowering may start 50-60 years after planting. When flowering, viable seed is produced that can be used for propagation. It is not advisable to propagate vegetatively from flowering clumps, as the new plants will also start flowering soon after planting. The overlapping of rhizomes in old clumps often raises the middle portion of the clump high above the ground.

Other botanical information
The culm size of G. apus can vary considerably. In Indonesia, local people use different names for plants with different culm sizes.

G. apus prefers the tropical humid lowlands, but also occurs on hill slopes up to 1500 m altitude. It is found in open areas, disturbed forest and on river sides on sandy or clayey soils. In drier areas culms remain smaller.

Propagation and planting
G. apus can be propagated by seed, when seed is available. It is, however, most commonly propagated by rhizome, culm or branch cuttings. Rhizome cuttings consist of fragments of young rhizomes bearing 1-2 culm buds. They are raised in a nursery and, when well rooted, are transplanted to the field at a spacing of 5-7 m2. Culm cuttings consist of culm segments or whole culms. Good results were obtained with 1-year-old culm segments bearing 2 buds each. The cuttings are set upright or at an angle, with the node well covered with soil. So far, no good results have been reported from treating cuttings with root-promoting substances. In Indonesia, the best time for planting is from December to March.

Once a clump has established normal care is required, including weeding. Application of organic or chemical fertilizer can be expected to increase productivity.

Diseases and pests
Rhizome cuttings often suffer seriously from rot fungi. G. apus is frequently attacked by a witches' broom disease caused by Epichloe bambusae, but without visible harmful effects on culm production. Dinoderus minutus is the most typical borer attacking harvested culms. Pest infestation of harvested culms is the most serious problem of G. apus.

The best time to harvest culms is during the dry season when the starch content is lowest (in Indonesia between April and October) so as to minimize borer infestation. Only culms of 2 years or older should be harvested.

It is estimated that a plantation of 1 ha can sustainably produce 6 culms per day during the dry season. In Indonesia, harvesting from April to October should provide an annual yield of about 1000 culms per ha.

Handling after harvest
After harvesting, culms are traditionally dried before use by leaning them against a large tree for a few days. Sometimes culms are immersed in running water or mud or, more recently, are treated with caustic soda, boric acid, chrome-arsenic acid formalin or borax-boron for preservation. To protect handicraft and furniture products, melamine or varnish is applied as a finishing.

Genetic resources and breeding
A small germplasm collection has been established in Lampung, Indonesia. Breeding programmes do not exist.

G. apus can be propagated and cultivated easily, and is very important for the handicraft industry, especially in Indonesia. More research is needed to obtain better culm preservation methods after harvest. Breeding programmes to obtain pest-resistant cultivars have also been suggested. It seems worthwhile to investigate whether this bamboo can be cultivated in other South-East Asian regions with ecological conditions comparable to Java's.

E.A. Widjaja

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