Dendrocalamus membranaceus Munro
Trans. Linn. Soc. 26: 149 (1868).
Gramineae
2n = 72 (hexaploid), 70
Origin and geographic distribution
D. membranaceus is native to Thailand (especially northern and northeastern), Burma (Myanmar) (eastern and down to Tenasserim) and Laos. For map click: Map516.TIF. It is occasionally cultivated in its native area and has been introduced in many botanical and private gardens (e.g. in Indonesia (Bogor, Lampung) and in India (Kerala)).
Uses
Culms of D. membranaceus are used for building purposes, bamboo board, furniture, basketry, matting and handicrafts, and as props for fruit trees. They are said to be very promising for the production of paperpulp. Young shoots are edible; they have a slightly bitter taste but are excellent for processing because they are nearly smooth and easy to handle. When administered to hamsters, the aerial part of the plant induced anti-implantation activity.
Production and international trade
D. membranaceus is produced and traded locally in its native area. No statistics are available.
Properties
At a moisture content of 102.5% green culms have a density of 551 kg/m3; dry culms have a density of 664 kg/m3 at 7.2% moisture content. The fibre length is 2-3(-4.5) mm. At culm moisture contents of 102.5% and 7.2% the modulus of elasticity is 2393 N/mm2 and 3697 N/mm2, the modulus of rupture 25.8 N/mm2 and 37.1 N/mm2 and the compression strength parallel to grain 39.7 N/mm2 (no data for 7.2%) respectively. The average fresh weight of young shoots is 1167 g and the edible portion is about 40%. After cooking, shoots are creamy-white and tender.
Botany
Sympodial bamboo, forming rather open clump. Culm very straight, 20-24 m tall, 6-10 cm in diameter, wall 6-10 mm thick, covered with white powdery deciduous scurf when young, turning green on maturity; internodes 22-38 cm long; nodes prominent, basal ones with aerial roots. Branches arising from all nodes, upper ones slender and drooping. Culm sheath 30-50 cm x 12-20 cm, glabrous or with appressed dark brown hairs; blade narrowly lanceolate, 25-40 cm x 2-3 cm, reflexed, brown hairy on both sides; ligule about 5 mm long, dentate; auricles dark brown, wavy, fringed. Leaf blade lanceolate, 12-25 cm x 1.5-2.5 cm, thin, pale, hispid above, hairy on the midrib beneath, margins scabrous, apex acuminate; sheath striate, ending in a callus, cleft nearly to the base; ligule very short, obtuse, hairy; auricles falcate, wavy-bristly, 1 cm long, purplish ciliate, very white hairy when young. Inflorescences on leafless branches, consisting of distant globular spinescent heads 2.5-5.0 cm apart and up to 2.5 cm in diameter; spikelet slightly compressed, 10-13 mm x 2-5 mm, glossy, nearly glabrous, with 2 empty glumes and 2-3 fertile florets. Caryopsis broadly ovoid, 5.0-7.5 mm long, grooved on one side and somewhat flattened, ending in a sharp point.
D. membranaceus sheds its culm sheaths very early. It flowers gregariously, in Thailand between October and April (dry season), but a flowering cycle is not known. In India it flowered in a botanical garden at an interval of 20 years.
D. membranaceus resembles glabrous forms of D. strictus (Roxb.) Nees and may easily be mistaken for it. It can be distinguished from the latter by its glabrous spikelets, thinner leaves, culm sheath with wavy hairy auricles, recurved apical leaf, and the more elongate grooved caryopsis.
Ecology
The natural habitat of D. membranaceus is a tropical mixed deciduous or monsoon forest below 1000 m altitude. In northeastern Thailand (Tak), where D. membranaceus is native, annual average minimum temperature is 21.7ºC (14.5ºC in January, 25.6ºC in April) and average maximum temperature 33.3ºC (30.5ºC in December, 38.1ºC in April); the average annual rainfall is 950 mm with a dry season from November to April.
Agronomy
D. membranaceus can be propagated by seed and by rhizome and culm cuttings. Fresh seed has a germination percentage of 90%. Seed remains viable for quite a long period (60% germination after 6 months); if stored at 4-5ºC, germination percentage was 80% after 6 months. Propagation by tissue culture is promising but still in the experimental stage. Planting is done in the rainy season. Young plants need watering in the dry season. No serious diseases or pests are known. The culms are rather resistant to culm borers but not to fungi. For construction purposes fully mature, 3-4-year-old culms are harvested, for basketry 2-year-old culms are used. Culms with the largest diameters are preferred for the bamboo board industry. After harvesting, culms are traditionally submerged in running water for 10-20 days. Preservation by boiling culms for 10-20 minutes in a solution of sodium carbonate, calcium hydroxide and copper sulphate is also practised. It takes about 3 months to air dry the culms. Mature culms dry with little cracking, immature ones are liable to collapse and shrink excessively. Culms used for weaving and handicrafts are cleaned by rubbing with ash, coconut husks or rice straw, which leaves the shiny surface undamaged; sandpaper cleaning is used for furniture. For furniture making, culms are roasted above fire at 110-130ºC for 15-20 minutes 2-3 times.
Genetic resources and breeding
A germplasm collection of D. membranaceus is available at the Centre bamboorium of Arunachal Pradesh in India. More collections are urgently needed from its native areas. There are no breeding programmes.
Prospects
Most of D. membranaceus resources in natural forests have been overexploited for many decades. Given the increasing demand for culms for local uses, studies on proper methods for cultivation, harvesting, and conservation are urgently needed. D. membranaceus is potentially of interest for the production of edible shoots in other South-East Asian countries.
S. Duriyaprapan and P.C.M. Jansen
For additional information about author(s) see Contributors or Editors.