Gigantochloa levis

Gigantochloa levis (Blanco) Merrill

Amer. Journ. Bot. 3: 61 (1916).
2n = unknown

Origin and geographic distribution
The origin of G. levis is unknown. It is commonly cultivated in the Philippines and in northern and western Borneo. In the Philippines it has apparently naturalized to a certain extent. For map click: Map520.TIF.

In the Philippines and Sabah, G. levis is best known as a bamboo which yields good quality edible shoots. The culms are used in rough house construction, as framework, and are split for plaiting walls. In the Philippines, modern furniture is crafted from the culms, and in the fishing industry, culms are used for making rafts, fish traps, outriggers and fish pens. It is also one of the several bamboos used in the handicraft industry. In Sabah, many specific uses of G. levis culms can be found, from temporary water pipes to fences and bathing platforms beside rivers. One Philippine study indicated that G. levis is suitable as raw material for kraft pulps from the standpoint of pulp strength, pulp yield and acceptable level of silica content.

Production and international trade
In the Philippines and northern Borneo production and trade of edible shoots and strong culms is locally important, but no statistics are available.

The fibre dimensions of the culms are: length 1.5-2 mm, diameter 16-22 µm, lumen diameter 4-6 µm, wall thickness 6-8 µm; number of fibrovascular bundles 1-2/mm2, vessel length 0.6-1.1 mm, vessel diameter 0.19-0.23 mm.
The moisture content of green culms ranges from 94-143%; specific gravity is 0.5-0.6. During drying from green to oven dry, culms shrink 9-13% in thickness and 5.8% in diameter.
For green culms the modulus of elasticity is 8900-11,000 N/mm2, modulus of rupture 20-26 N/mm2, compression strength parallel to grain 38-44 N/mm2 (with nodes), 39-43 N/mm2 (without nodes).
The chemical composition of mature culms on dry weight basis is approximately: holocellulose 63%, pentosans 19%, lignin 24%, ash 5.3%, silica 2.8%. The solubility is 3.2% in alcohol-benzene, 4.4% in hot water and 28.3% in 1% NaOH. Per 100 g edible portion young shoots (7-15 days old) contain approximately: water 87 g, protein 3 g, fat 7 g, carbohydrates 0 g, fibre 1.5 g, ash 1 g, Ca 30 mg, P 27 mg, Fe 1 mg, thiamine 0.07 mg, vitamin C 4 mg.

Densely tufted, sympodial bamboo. Culm erect, up to 20 m tall, diameter up to 16 cm or possibly slightly more, plain green; nodes not conspicuously swollen; internodes up to 45 cm long, densely dark-hairy all over at the base of the culm, otherwise scattered dark-hairy on the upper parts, without any conspicuous white waxiness. Branches at each midculm node arising from a single bud consisting of a dominant primary branch, with usually one subdominant secondary branch from its base on each side, and several lesser leafy branchlets from the base of secondary branches. Culm sheath broadly triangular, 19-34 cm long, pale to medium green, with dark brown hairs on the back; blade broadly lanceolate, green, spreading to reflexed, hairy at base; ligule lacerate, the base 2-4 mm long, the lacerations 7-15 mm long; auricles large lobes to 10 mm long, with bristles 5-20 mm long on the margin, dark green to purplish green. Young shoot slightly triangular in outline, brown-green to green, covered with dark brown hairs, with green tips. Leaf blade 8-35 cm x 2-7 cm, lower surface short pale-hairy; ligule a subdentate rim-like structure 0.5-1.5 mm long; auricles small lobes with fine bristles to 4 mm long on the margin. Inflorescences, usually on leafless culms, consist of puberulent long branches with clusters of up to 75 pseudospikelets at the nodes, the clusters 1.5-12 cm apart; pseudospikelet 10-12 mm long, with 2-3 gemmiferous bracts, 2-3 glumes, 4-5 perfect florets and a vestigial terminal floret usually represented by an empty lemma. Caryopsis unknown.

Growth and development
From a plantation started with culm cuttings, the following observations are available from the Philippines (average of 7 clumps): number of culms increased from 3.6 (1.5 years after planting) to 4.3 (3 years after planting) and to 9.4 (5 years after planting); the average height increased from 3.7 m to 5.5 m and to 10.4 m, and the average diameter from 2 cm (1.5 years planting) to 11 cm (5 years after planting). The average number of young shoots per clump per year increased from 2 (first year) to 2-4 (3rd year), to 3-5 (4th year), to 7-9 (6th year) and to 10-15 (10th year after planting).
An average of 31% of culms produced by a mature clump reach maturity. Full height is achieved by new culms in approximately 5 months, which means an average daily growth rate of about 13 cm. In the Philippines, young shoot growth starts at the beginning of the rainy season but is most rapid in the latter part of the season (up to 2.73 m per week). In a G. levis plantation in Mindanao (Davao Del Norte) an average of 40 culms per mature clump was counted, of which 11 (about 28%) were one year old and the rest older.
Flowering occurs over many months in a fertile clump, in one to several or all culms. After flowering, culms senesce, but sometimes clumps regenerate from the rhizome.

Other botanical information
G. levis can be distinguished from G. thoii K.M. Wong of Peninsular Malaysia with which it has been confused, by the less hairy and copiously white-waxy culms of the latter.

G. levis grows reasonably well on a large range of sites, except where the soil is too sandy or too dry. In the Philippines it occurs in secondary forest and abounds in and around towns and villages in the lowland.

Propagation and planting
G. levis is propagated only vegetatively, usually by rhizome or culm cuttings. For culm cuttings it is recommended to take pieces of about 50 cm in length, including a well-developed branching node, and to plant it horizontally at 10 cm depth. Cuttings are planted first in a nursery or, as documented in the Philippines, directly in the field, at the onset of the rainy season. The recommended spacing for a plantation is 6-7 m x 7 m, which will result in about 200-240 plants per ha.

Newly planted material is very susceptible to drying out and requires regular watering. Per ha 20-30 kg N, 10-15 kg P, 10-15 kg K, 20-30 kg silica, and compost are recommended to stimulate growth, given in two applications, 1 and 5 months after planting. Weeding is important until the bamboo canopy is fully established. Malformed, diseased or otherwise useless culms should be removed.

Diseases and pests
In Borneo, severe infestations of witches' broom have been observed in some populations of very old clumps. These clumps may have flowered previously, and the culms may be physiologically weakened and therefore more susceptible to attack by disease.

Shoots can be harvested 7-15 days after emergence. Whereas younger shoots have less protein and fat and more iron, they also have much less crude fibre per 100 g edible portion. Because the best texture in shoots is present just one week after emergence, that may also be the best time to harvest. Culms of about a year old can be harvested for making handicrafts, but only culms of at least 3 years old should be taken for construction purposes. It has been estimated that a clump should only be harvested 5-8 years after planting, and not more than 60% of all standing mature culms should be harvested from any clump per year.

In the Philippines the annual yield per ha from a plantation belonging to the Davao Fruits Corporation (Davao del Norte, Mindanao), was estimated at 9300 culms of average 6.5 cm in diameter and 16.7 m in height. These dimensions suggest that clumps were not in their best condition and may reflect detrimental effects of the past overharvesting. The culm dry-weight production for this plantation was estimated at 115.8 t/ha.

Handling after harvest
In the Philippines, the shoots of G. levis are marketed fresh, pickled or dried. In Sabah, shoots are sold fresh or pickled. Harvested culms apparently are more durable and resistant to insect and fungal attack if they have been immersed in water for about 60 days. In some cases in the Philippines, prior to use, culms are sun-dried (for 4 weeks or more) or kiln-dried (for about 9 days) and then subjected to curing with smoke or painted with slaked lime ('whitewashing'). Another method of traditional curing is to leave the branches and leaves on a harvested culm for some time, which is said to reduce the amount of moisture and starch in the culm via transpiration through the leaves. Of the various chemical methods of preservation suggested as suitable, painting the culms with a water emulsion of 0.5-1% gamma benzene hexachloride requires the least capital investment. In spite of these preservation methods, G. levis culms are said to have moderate natural durability.

Genetic resources and breeding
Populations raised from seed are not known or else not properly documented. Material from each provenance is apparently raised from clonal stocks and therefore of limited genetic variability. These aspects cannot be clearly elucidated without precise information on reproductive biology.

G. levis is a large-diameter useful bamboo that can provide both good edible shoots and strong culms. It is already commonly but usually casually cultivated in the Philippines and northern Borneo. This bamboo is among the best candidates for cultivation and exploitation, though clearly more information on its agronomy and use is desirable.

K.M. Wong

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