Dicranopteris linearis (PROSEA)
Dicranopteris linearis (Burm.f.) Underw.
- Protologue: Bull. Torrey Bot. Club 34: 250 (1907).
- Family: Gleicheniaceae
- Chromosome number: 2n= 78 (diploid), 117 (triploid), 156 (tetraploid)
Dicranopteris dichotoma (Thunb. ex Murray) Bernh. (1806), Gleichenia hermannii R. Br. (1810), G. linearis (Burm.f.) Clarke (1880).
- Scrambling fern, false staghorn (En)
- Indonesia: resam (Indonesian), hasam (Lampung), paku andam (Sundanese)
- Malaysia: resam, bengakawang (Malay), máng ch'í (Chinese)
- Philippines: kilob, tilub (Tagalog), gapingoi (Bontok)
- Thailand: kiku kachoei (northern), kut pit (northern), kut taem (peninsular).Vietnam: tế, guột, ráng tây sơn ngay.
Origin and geographic distribution
D. linearis is an Old World tropical and subtropical species, occurring from Africa to Taiwan and throughout South-East Asia to Australia, New Zealand and Polynesia (as far as Hawaii). In South-East Asia it is one of the most common ferns.
Although D. linearis is sometimes considered a weed, its pliant fibrous leaf stems (petiole and leaf axis) are widely used in Asia for various purposes. The lignified peripheral fibres of the stem are used for plaiting. The whalebone-like pith that comes loose from the peripheral fibres is brittle near the base but flexible and resilient at the top and is used for pretty and elegant plaiting. Fishing-stakes, baskets and sometimes ropes have been made from the stems. They are quite resistant to salt water and therefore the fern is widely used in the construction of fish-traps where the stems last for about two years. D. linearis is sometimes planted to prevent soil erosion. The stems have also been used to make seats of chairs and stools, mats, pouches, hats, cigar cases, caps and to form woven partition-walls for houses. The caps ("songko"), used in northern Peninsular Malaysia and peninsular Thailand, are durable enough to last several generations. In Malaysia they are sometimes coated with wood-tar to make them more durable. In Papua New Guinea arm bands and belts are made from the stems and the plants are used for casual adornment. The very firm stems can be sharpened to a resistant point. In Malaysia they were shaped into pens ("kalam") used for Arabic calligraphy. The oldest and strongest stems make the best pens and they have also been used to make knives. In Indonesian nursery gardens entire leaves are put upright in the ground to shade young crop plants. By the time the young plants can stand exposure to direct sunlight, the fern leaves have wilted and shed their foliage. D. linearis also has several traditional medicinal uses. Crushed leaves are applied as a poultice or drunk as an infusion to combat fever. Apparently, high doses are harmful and decoctions are applied externally as a cooling lotion rather than drunk, unless they are prepared from young leaves or in a low dose in combination with other ingredients. The fern has also been used to cure chest complaints such as asthma and cough, and to cure bruises, burns and sprains. In Indo-China D. linearis is considered anthelmintic. In northern Thailand, decoctions are drunk against insomnia and used to bathe children with bad skin rash and people with a broken leg. Together with Shorea leaves the leaves are used to treat itching caused by stinging hairs of Urticaceae . In Papua New Guinea the leaves are plastered on wounds. In Hawaii the plant is soaked in water and the extract is drunk to cure constipation.
Production and international trade
At the beginning of the 20th Century, Peninsular Malaysia exported vigorous stems of D. linearis on a small scale to India. Production and trade is mainly local and is dying out as the ready-for-use fibres for matting and weaving are very expensive.
The leaves of D. linearis contain tannins (3.8%), essential oils (0.03%) and saponins. They also contain clerodane glycosides. Flavonoids are limited to flavonol 3-O-glycosides, such as afzelin, quercitrin, isoquercitrin, astragarin, rutin and kaempferol. The 13 varieties of D. linearis differ in chemical constituents, each variety containing at least one different flavonol or flavone.
D. linearis plants concentrate relatively high levels of rare earth elements, especially in the roots (Eu, Gd, Ho, Pr, Sm, Y) and the leaves (Ce, Dy, La, Nd, Tb). The lanthanum replaces the magnesium position in chlorophyll and coordinates with the porphyrin ring. The lanthanum has been observed to have a similar coordination structure to a sandwich-type lanthanide complex ("double decker sandwich structured La-substituted chlorophyll a"), with the La surrounded by eight nitrogen atoms from two porphyrin rings with an average La-N bond length of 2.65 Angstrom.
Tests in the Philippines revealed that water extracts of D. linearis showed positive antimicrobial activity against Micrococcus luteus and Escherichia coli .
A terrestrial thicket fern, up to 3 m tall, with dichotomously divided leaves. Rhizome several m long, up to 5 mm in diameter, creeping, brown, bearing septate, branched hairs. Leaves 2-3-furcate, with only the ultimate branches bearing pinnae, in addition to a pair of stipule-like pinnae (accessory branches) at the basis of each bifurcation, spaced 6-20 cm apart on rhizome; petiole erect, stout, 10-100 cm or longer, lustrous brownish to purpuraceous, glabrous; lamina of complex three-dimensional shape, 60-200 cm long, bearing hairs, especially near bases of the midribs and minute, oblong-obtuse brown glands along the veins; rachis sometimes very long, at the bifurcations with a dormant bud, with brown, branched hairs, glabrescent; pinnae narrowly lanceolate, deeply pinnatifid, asymmetrical at base, more reduced towards the acute to acuminate apex; ultimate segments linear, 18-40(-70) mm × 3-5 mm, confluent at the broadened base, apex obtuse or emarginate, glabrous. Sori superficial, in a median row on each side of the midrib, subcircular, 1 mm in diameter; sporangia without indusia. Spores trilete, tetrahedral with prolonged angles, somewhat wrinkled.
Growth and development
Spore germination of D. linearis is by a thread-like body with transverse divisions. The gametophyte is long-lived, subcordate to ribbon-like, with a thick central strand. The archegonia are long-necked and curve forward, the antheridia many-celled and scattered over the lower surface. Two-celled hairs are frequent. The prothalli grow in enormous numbers in slightly sheltered places on bare earth banks and other exposed positions where other prothalli would not survive. After fertilization the sporophyte starts growing, reaching 2-3 m in height. The leaves of D. linearis eventually grow so long that they cannot support themselves in an erect position and so they form a tangled thicket which is extremely difficult to cut through.
Other botanical information
Gleicheniaceae is an old, rather isolated family, perhaps dating back to the Carboniferous, comprising 5 genera. Dicranopteris Bernhardi comprises about 12 species, most strongly represented in South-East Asia with 5 species. D. linearis is a very variable species and many varieties have been described. In South-East Asia 13 varieties are distinguished, mainly based on the mode of branching (e.g. equal or unequal branches, angle of branching), the presence or absence of stipule-like pinnae, hairiness and number of veins. Some of them are more distinct than others and should perhaps be considered as species. The existence of a triploid hybrid indicates that it is probably impossible to refer every plant to a clearly defined variety. It is questioned whether D. linearis is conspecific with the neotropical D. flexuosa (Schrad.) Underw. D. curranii Copel., occurring in Thailand, Malaysia, Indonesia (Sumatra, Kalimantan, Java, Flores, Sulawesi) and the Philippines (ultimate branches are commonly 40 cm × 9-12 cm) is in general somewhat larger than D. linearis but is similarly used. It was described formerly as one of the varieties of D. linearis and for purposes of matting it is even considered better.
Gleichenia flabellata R. Br. (shiny fan fern, umbrella fern), occurring in New Guinea, Australia, New Caledonia and New Zealand, has a similar positive effect as Dicranopteris on soil erosion prevention and is sometimes planted for that purpose.
D. linearis forms dense thickets over large, dry, sunny areas with poor soils, from sea-level up to 2800 m altitude. The indeterminate growth form, the shallow rhizomes, the leaves with low decomposability and its mat-forming capacity enables it to colonize sites and to maintain dominance. After clearing of steep hillsides, it soon covers the open site, preventing landslides during torrential downpours. It is, however, less resistant to cutting and fire than Pteridium which penetrates much deeper into the soil. Dicranopteris stands offer a suitable microhabitat for the germination of tree seed, but they also outcompete saplings. Its rapid spread makes D. linearis a noxious weed in plantations. It can be combatted biologically by some insects, manually by repeatedly removing the rhizomes and chemically by spraying for example paraquat (600 g/ha). Although warm conditions are preferred, it survives in cooler climates but is sensitive to frost. It is highly efficient in extracting P from the soil which enables it to colonize sites poor in P. In Hawaiian sites it contributed up to 74% of the aboveground net primary production where it constituted only 14% of the live biomass. Where it contained only 24% and 30% of plant N and P, it accounted for up to 57% and 47% of total N and P uptake, respectively. Its leaves are short-lived but slow to decompose, even under high temperature and rainfall conditions. More than 50% of the original leaves and more than 77% of the stem mass may still remain after more than two years. The slow decomposition is related to the lamina which remains unabscised on top of the petiole and the high lignin-nitrogen ratio (56-129). As a result it is a major contributor to soil detrital pools; fixed carbon is quickly transferred to the soil where it contributes to the organic matter and makes conditions more oligotrophic.
Propagation and planting
D. linearis is quite difficult to raise from spores, although this has not been tried frequently. It is difficult to know when sporangia are fully mature and ready for collection. However, propagation by planting rhizome pieces in poor soils exposed to full sun is easy and effective. D. linearis is easily killed in fertile soils with excessive mineral supply and for this reason it is seldom found in botanical gardens or otherwise cultivated.
Handling after harvest
Harvested stems of D. linearis are longitudinally cut into four pieces and soaked in water for 7 days and then rubbed with coconut oil to obtain a black colour. The pith fibres are easily separated by bruising the stem or by cutting them longitudinally. After soaking for two days the fibres turn a light brown colour. The plaiting must be done when the fibres are still wet because when dry they are too brittle. For fish-traps the hardest stems are selected, joined in bundles and carefully dried in the sun for a week until the colour of the stems changes into an even, shining dark brown.
Genetic resources and breeding
D. linearis is widely distributed and does not seem to be in danger of extinction. No germplasm collections or breeding programmes are known to exist. The genetic variability may be less than suggested by its abundance as many populations consist of few genotypes covering substantial areas. Since the chemical composition is dependent on the variety, loss of variability could pose a risk of losing properties, but none of the Southeast-Asian varieties are confined to a limited area.
Due to more easily available alternative fibre material, the use of D. linearis is declining. Possibly, more attention is now paid to its eradication as a troublesome weed than to its useful properties. Locally it will remain of importance as a fibre source but no new developments are foreseen. The medicinal uses deserve further investigation.
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