Blechnum (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Blechnum L.

Protologue: Sp. pl.: 1077 (1753), Gen. pl.: 560 (1754).

Family: Blechnaceae

Chromosome number: x= 28-40 (diploids, triploids and tetraploids occur);B. indicum: 2n= ca. 74;B. orientale: 2n= ca. 64-66

Major species and synonyms

• Blechnum egregium Copel., Perkins, Fragm. fl. Philipp. 3: 187 (1905), synonym: B. nitidum C. Presl var. contracta Hook. (1860). Note: The name B. insigne Copel. has been used formerly, but it is a nomen nudum.

• Blechnum indicum Burm.f., Fl. Indica: 231 (1768), synonyms: B. striatum R. Br. (1810), B. moluccanum Desv. (1811), B. malaccense (C. Presl) Fée (1852).

• Blechnum orientale L., Sp. pl.: 1077 (1753) (erroneously as B. occidentale L., corrected in 2nd ed.: 1535 (1763), synonyms: B. javanicum Blume (1828), B. adnatum Reinw. ex De Vriese (1846), Blechnopsis orientalis (L.) C. Presl (1849).

• Blechnum vittatum Brack., U.S. expl. exped. 16: 131 (1854), synonyms: B. dentatum (Kuhn) Diels (1901), B. bamlerianum Rosenst. (1912), Lomaria bamleriana (Rosenst.) Alderw. (1917).

• Blechnum vulcanicum (Blume) Kuhn, Ann. Mus. Bot. Lugd.-Bat. 4: 284 (1869), synonyms: Lomaria vulcanica Blume (1828), L. villosa Fée (1852), Spicanta vulcanica (Blume) Kuntze (1891).

Vernacular names

• B. egregium
• Papua New Guinea: hariga (Orokaiva)
• Philippines: patugo (Manobo).

• B. indicum
• Indonesia: bacai, paku paci besar (Kalimantan), kadu (Irian Jaya).

• B. orientale
• Indonesia: paku leucir, paku lipan, paku lubang
• Malaysia: paku lipan, paku ikan (Malay), kelindang (Sarawak)
• Papua New Guinea: aduba, zani (Orokaiva)
• Philippines: pakong alagdan (Tagalog)
• Thailand: kut khang fan (northern), kut doi (central), mahasadam (south-eastern)
• Vietnam: ráng dừa dông, cây răng dê lá dừa.

• B. vulcanicum
• Indonesia: paku gunung.

Origin and geographic distribution

Blechnum is an early group of ferns, probably originating from late Cretaceous, with a radiate distribution pattern centred on Gondwanaland with distinctive but overlapping lines of speciation extending northwards from Antarctica. At present it is a widespread genus comprising about 180 species, most of which occur in the southern hemisphere; in South-East Asia about 20 species are present. B. egregium is widespread throughout the Philippines and it occurs also in some isolated localities in Sabah (Malaysia) and Papua New Guinea. B. indicum is distributed from continental South-East Asia through Sumatra, (not found in Java), Borneo and New Guinea to New Caledonia and northern and eastern Australia. B. orientale is the most abundant and most widespread species and is found from India, Nepal and southern China throughout South-East Asia to southern Japan, Australia and Polynesia. B. vittatum occurs from eastern Papua New Guinea and the Solomon Islands to the Santa Cruz Islands. B. vulcanicum is rarely common and occurs from non-continental South-East Asia and Australia to New Zealand, through the Pacific as far east as the Cook Islands and north to the Marquesas.

Uses

Tender portions of young leaves of all Blechnum species are eaten as a vegetable in the Philippines and Papua New Guinea. They are also cultivated as an ornamental because they are elegant and beautiful with brilliant scarlet young leaves and dark green upper and paler lower surfaces in mature leaves. In some places the croziers are considered a delicacy, somewhat resembling asparagus in flavour and texture. On Frederik Hendrik Island off the coast of Irian Jaya (Indonesia), a coarse edible flour is prepared from the rhizome. In Australia the rhizome is washed, roasted, ground or pounded, sclerotic leaf and root traces removed and the resultant flour made into a kind of unleavened bread. In the Philippines, B. orientale is used as an ingredient in stews. In Papua New Guinea young leaves are eaten as a wild food supplement, but they are also used to induce sterility in women. Total sterility can be achieved by eating new leaves for three successive days, waiting a fortnight and repeating the treatment. In Malaysia and the Philippines the rhizome is also consumed for food whereas in the Philippines it is used as a diaphoretic, aromatic, aperative, and a poultice made from the leaves is a recommended treatment for boils (also in Peninsular Malaysia). In India and Polynesia the rhizome is used against intestinal worms and bladder complaints. In Chinese pharmacies the rhizome is prescribed in relation to urinary complaints. In Malaysia B. orientale is a magical application for dropsy, along with the leaves of Elephantopus scaber L. (prickly-leaved elephant's foot, a tropical weed of Compositae (see Prosea 12(1), which possesses numerous interesting medicinal properties, including being useful against dropsy). On Waya Island (Fiji) new brightly coloured leaves are used as necklaces.

Production and international trade

Blechnum plants are not cultivated commercially but they are locally important. Fresh croziers and young leaves of B. indicum are sold in bunches on many local South-East Asian markets and in some countries the croziers are canned and sold as a delicacy.

Properties

In the Philippines, per 100 g edible portion, the young, unexpanded leaves of B. orientale and B. vulcanicum contained respectively: total N 1.36 g and 1.33 g, P 156 mg and 181mg, K 625 mg and 475 mg, Ca 206 mg and 343 mg, Fe 16 mg and 45 mg, Mg 290 mg and 842 mg. Flavonoid glycosides and the four lignans blechnic acid, 7-epiblechnic acid, 8-epiblechnic acid and brainic acid were isolated from a number of fern species including B. orientale . Tests in the Philippines showed that water extracts of B. orientale possessed antifungal properties against Bacillus subtilis, Candida utilis, Escherichia coli, Micrococcus luteus, Pseudomonas aeruginosa and Staphylococcus aureus .

Description

Rhizome or caudex ascending to erect, thick, densely covered with narrow, dark brown, lustrous scales; some species eventually forming a short trunk up to 2 m tall, usually forming extensive colonies interconnected in the early stages of development by rhizomes or stolons. Leaves all similar or fertile leaves different, pinnate, pinnatifid or pinnatisect, rarely simple, bipinnate or multipinnate; sterile leaf subcoriaceous, glabrous, pinnae linear, entire to dentate, veins free; fertile leaf similar to the sterile leaf or with much narrower pinnae. Sori at the underside of the pinnae, linear, closely aligned to the midrib, in reduced pinnae covering the entire surface; indusium narrow, opening towards the midrib. Spores monolete, bilateral, reniform to subglobulose, with various decoration patterns.

• B. egregium . Caudex up to 100 cm long, 5-10 cm or more in diameter; scales linear triangular with a finely acuminate apex, up to 3 cm × 2 mm, entire, shiny dark brown to black. Leaves dimorphous, pinnate; petiole 3.5-31 cm long, brown, darker at the base, densely and persistently scaly; sterile lamina narrowly elliptical or ovate to narrowly elliptical in outline, 20-120 cm × 9-30 cm, gradually narrowed towards the base, apex acute, rachis and veins dark to reddish-brown, or paler, at underside with two lateral grooves, sometimes at upperside persistently scaly; pinnae narrowly triangular, middle ones 2.5-15 cm × 0.8-2 cm, base adnate to the rachis, margins crenate to serrulate, dentate near the apex, apex acuminate to attenuate; fertile lamina of the same size as the sterile ones or somewhat larger; fertile pinnae restricted in width or not, widening a little towards the rachis becoming broadly adnate and decurrent. Sori in narrow pinnae occupying the whole undersurface, in normal pinnae restricted to either side of the midrib. Spores 48 μm × 36 μm, smooth to granulose.

• B. indicum . Rhizome very variable, from slender and creeping to an erect caudex, covered with old leaf bases and adventitious roots or with small scales; scales 3-4 mm × 1 mm. Leaves all similar, pinnate; petiole 6-50(-83) cm long, very dark at the base to brown or stramineous towards the top, scales persistent only at the very base; lamina ovate to narrowly elliptical in outline, up to 50(-100) cm × 6-15(-28) cm, base acute, apex acuminate, rachis stramineous, usually glabrous and lustrous; pinnae in 16-52 pairs, oblong to narrowly elliptical, 4-16.6 cm × 0.5-1.6 cm, base cordate, sessile or shortly petiolate, articulate to the rachis with a characteristic socket joint, margins serrate, gradually narrowing into the acuminate apex, veins up to twice forked, very fine and close, 3-4 per mm. Sori close to and often covering the midrib, usually extending to the pinna base but not to the apex, indusium nearly 1 mm wide. Spores 36 μm × 28 μm, light brown, minutely papillate.

• B. orientale . Rhizome forming a stout suberect caudex, 6-20(-300) cm long and 4-5 cm in diameter, densely covered with scales; scales linear-elliptical, up to 2 cm × 2 mm, dark brown with pale margins. Leaves all similar, pinnately divided (in juvenile plants pinnatifid), rarely bipinnate or multipinnate; petiole up to 70 cm long, stramineous or purplish when young, densely scaly at the base, bearing small auricles (also considered as reduced pinnae and then petiole only 5 cm long) throughout about 3 cm apart; lamina lanceolate to ovate in outline, up to 200 cm × 54 cm, rachis pale pinkish-brown, glabrous or with a few hairs and slender, brown scales; pinnae 6-70 or more pairs, 2-5 cm apart, sessile, linear, 30 cm × 1.2-2 cm, base truncate or broadly cuneate, the upper ones decurrent, entire, gradually narrowing into the acuminate apex, veins simple or forked, distinct, spreading at a broad angle to the midrib and up to 0.5 mm apart at the midrib. Sori closely parallel to and on either side of the midrib, 1-2 mm wide, often enlarged to overlap or cover the midrib, indusium usually broken before maturity. Spores 47 μm × 37 μm, pale translucent with a clear, rather narrow median wing, smooth to scabrous.

• B. vittatum . Caudex erect or suberect, up to 1 m long and 3-5 cm in diameter, densely scaly at the apex; scales linear-acuminate, 1-4 cm × 0.2-1.5 mm, black or very dark brown, frequently with paler margins. Leaves usually dimorphous, pinnate; petiole 12-58 cm long, dark at the base, stramineous upwards, densely and persistently scaly at the base, few scales persistent elsewhere, petiole and rachis at underside often with conspicuous black lines on the ridges on either side of the groove; lamina in outline ovate to narrowly elliptical in smaller (50 cm long) leaves, linear to narrowly elliptical in larger (100 cm) ones, up to 100 cm × 40 cm, base more or less truncate, gradually widening towards the middle, apex acute; rachis stramineous to pale brown, glabrous or with a few scales; sterile pinnae oblong to narrowly elliptical, 6-21 cm × 1-2 cm, base adnate and often decurrent (middle region of the lamina), often slightly auriculate, in larger leaves several basal pairs may be petiolate and deflexed, margins crenate to denticulate, increasingly toothed towards the sharply acute apex; fertile pinnae similar to the sterile ones, or narrower and linear, 15(-20) cm × 2.5-3.5 mm, with veins simple or forked, distinct, ending in a gland. Sori covering the whole surface when the fertile pinnae are narrow, in normal pinnae sori not covering the whole undersurface, often somewhat discontinuous. Spores 46 μm × 33 μm, smooth to scabrous.

• B. vulcanicum . Rhizome creeping or erect, often forming a caudex up to 20 cm long and 3 cm in diameter, clothed with densely scaly bases of old petioles; scales linear to narrow triangular, up to 2.5 cm × 3 mm, entire, shiny red-brown. Leaves dimorphous, erect or pendulous, narrowly to broadly elliptical in outline, 10-70 cm × 3-30 cm, fertile leaves usually longest, but size of leaves (and whole plants) varies considerably; petiole 5-40 cm long, slender, yellowish-brown, usually pilose with fine straight uniseriate hairs, at base densely persistently scaly; lamina pinnatisect to pinnate with 6-30 pairs of pinnae, rachis and veins with persistent whitish hairs; sterile pinnae oblong to narrowly triangular, often slightly falcate, 4-8 cm × 0.7-1.5 cm, sessile and adnate to rachis (except basal pair which is semi-adnate); fertile pinnae 4-8 cm × 4-6 mm wide, spaced on the rachis, margin often with hairs. Sori covering whole undersurface, indusium sometimes bearing hairs. Spores 42 μm × 33 μm, smooth to granulose.

Growth and development

After germination of a spore of Blechnum , a gametophyte is developed. The prothallus is cordate or elongate with a distinct firm midrib and often bearing simple chlorophyllous hairs. The gametangia are of the common, advanced leptosporangiate type. After fertilization the sporophyte starts growing and the first leaves are small and differ from the leaves in mature plants. Some species produce a caudex (stem) sufficiently tall for the plants to be regarded as small tree-ferns (e.g. most species mentioned here). Other species form a slender creeping rhizome which may be either aboveground or subterranean giving rise to colonies from one individual (e.g. sometimes B. indicum ), whereas other species produce a massive subterranean rhizome. In B. egregium the fertile leaves are seasonal in their development and usually occur in the central part of the leaves. In B. orientale the growth form varies from small leathery fertile plants on dry exposed soil banks to large harsh ferns of open spaces on the margins of lowland.

Other botanical information

In 1753 Linnaeus mixed up collections and described the most widespread species of the New World, B. occidentale L., as occurring in the Old World, and the most widespread species in the Old World, B. orientale L., as occurring in the New World. In 1763 he corrected the error and it has been generally accepted to have the correction effectuated starting 1753. Taxonomically, Blechnum is very incompletely known. It is classified in the Blechnaceae which comprises 9 genera (including Woodwardia J.E. Smith, mostly distributed in the northern hemisphere). The leaf pattern is a very important characteristic for identifying species in Blechnum , but sometimes characteristics of petiole, rachis, scales on the midrib, spores and hairs are also needed. B. egregium and B. vittatum are closely related; they can be distinguished by their basal pinnae: sessile or shortly petiolate but of normal size in B. vittatum , reduced to small, (semi)adnate lobes in B. egregium . B. indicum is closely related to the American B. serrulatum Rich. with broader and oblong pinnae that do not taper evenly from the base to the apex. B. orientale occupies a very wide range of habitats resulting in extremely varying plants, from 20 cm up to over 3 m tall. Sometimes confusion with B. finlaysonianum Wall. is possible, but the latter always grows in the shade, having pinnae up to 4 cm wide and not tapering towards the apex. B. vulcanicum plants are very variable in leaf size and hairiness; in Malesia plants are usually densely brown pilose but plants with paler, often silvery white hairs also occur. It is possible that what is known as B. vulcanicum from outside Malesia, is a complex of several species. B. gibbum (Labill.) Mett. (dwarf tree fern) is raised in nurseries and sold as a pot plant in West Java.

Ecology

The greatest diversity of Blechnum species is to be found in almost perpetually humid regions. In South-East Asia all species are primarily terrestrial, although in very humid habitats some individuals might grow on fallen logs. B. egregium is mostly found in humid jungle areas on stream banks and protected cliffs, from the lowland up to over 1500 m altitude. B. indicum grows in brackish swampy areas and river margins, usually near the coast but sometimes inland and up to 1900 m altitude, often forming extensive dense stands on sandy or peaty soils in open, sunny locations, usually along with grasses. B. orientale is often a primary colonizer after forest clearing and fire and it sometimes becomes a dominant species after repeatedly being burnt. It is a fern of open places which never grows in the shade. On very exposed sites the plants may be stunted with often unusually wide sori. It is found from the low hills up to 1500 m altitude. B. vittatum is a forest fern and a common undergrowth species from the primary and secondary lowland rain forest up to 600 m altitude in Fiji and up to 1200 m in Papua New Guinea. It may invade volcanic slopes within two years after an eruption. B. vulcanicum grows in cool, moist, partly shaded locations, usually in forest, more rarely in exposed tall grasslands. It is certainly not restricted to volcano sides.

Propagation and planting

B. orientale grows easily from spores. In culture, 95% of the spores germinated 30 days after sowing. No information is available on commercial cultivation.

Husbandry

When B. orientale is planted in gardens, the soil should be well drained. Provided the plants are well watered, they can be exposed to the full sun. Plants can be grown within the temperature range 8-40°C.

Diseases and pests

The fungus Stenella australiensis was found to attack B. indicum in Australia.

Genetic resources and breeding

Germplasm collections or breeding programmes are not known to exist for Blechnum .

Prospects

Blechnum comprises a range of interesting species with variable uses including edible young leaves and rhizomes as well as medicinal applications. The ornamental value of several species may have commercial potential. More research is needed to evaluate the possibilities for domestication and to determine the food value of the edible species and the active principles of the medicinal species.

Literature

• Amoroso, V.B., 1990. Ten edible economic ferns of Mindanao. The Philippine Journal of Science 119(4): 295-313.
• Chambers, T.C. & Farrant, P.A., 2001. Revision of Blechnum (Blechnaceae) in Malesia. Blumea 46: 283-350.
• Holttum, R.E., 1966. A revised flora of Malaya. 2nd Edition. Vol. 2. Ferns of Malaya. Government Printing Office, Singapore. pp. 444-449.
• Johnson, A., 1960. A student's guide to the ferns of Singapore Island. University of Malaya Press, Singapore. pp. 78-80.
• Kramer, K.U., Chambers, T.C. & Hennipman, E., 1990. Blechnaceae. In: Kramer, K.U. & Green, P.S. (Volume editors), 1990. Pteridophytes and gymnosperms. In: Kubitzki, K. (Series editor): The families and genera of vascular plants. Vol. 1. Springer-Verlag, Berlin, Germany. pp. 60-68.
• Tagawa, M. & Iwatsuki, K. (Volume editors), 1979-1989. Pteridophytes. In: Smitinand, T., Larsen, K. (Series editors): Flora of Thailand. Vol. 3. Forest Herbarium, Royal Forest Department, Bangkok, Thailand. pp. 297-302.
• Umi Kalsom, Y., 1994. Flavonoid glycosides in the fern Blechnum orientale Linn. American Fern Journal 84(2): 69-70.
• Wada, H., Kido, T., Tanaka, N., Murakami, T., Saiki, Y. & Chen, C.-M., 1992. Chemical and chemotaxonomical studies of ferns 81. Characteristic lignans of blechnaceous ferns. Chemical and Pharmaceutical Bulletin Tokyo 40(8): 2099-2101.
• Zamora, P.M. & Co, L., 1986. Guide to Philippine flora and fauna. Vol. 2. Economic ferns, endemic ferns, gymnosperms. Natural Resources Management Center, Ministry of Natural Resources and University of the Philippines, Goodwill Bookstore, Manila, The Philippines. pp. 50-52.

Authors

F.X. Inawati