Adiantum (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Adiantum L.

Protologue: Sp. pl.: 1094 (1753); Gen. pl., ed. 5: 485 (1754).

Family: Pteridaceae

Chromosome number: x= 30 (many aneuploids and polyploids exist);A. capillus-veneris: 2n= 60, 120;A. caudatum: 2n= 60, 90, 120;A. philippense: 2n= 60

Major species and synonyms

• Adiantum capillus-veneris L., Sp. pl.: 1096 (1753).

• Adiantum caudatum L., Mant. pl.: 308 (1771), synonyms: A. hirsutum Bory (1804), A. ciliatum Blume (1828), A. malesianum Ghatak (1963).

• Adiantum flabellulatum L., Sp. pl.: 1095 (1753), synonym: A. bonii Christ. (1894).

• Adiantum philippense L., Sp. pl.: 1094 (1753), synonym: A. lunulatum Burm.f. (1768).

Vernacular names

• General: maidenhair ferns (En). Chevelure, sieplier (Fr)
• Indonesia: suplir
• Vietnam: chi tóc vệ nữ.

• A. capillus-veneris . Venus hair fern, common maidenhair fern (En). Southern maidenhair (Am)
• Philippines: kulantrillo de Alambre, lettuce de Alambre
• Thailand: foen kan dam (central), kut pha (northern), phak waen han (eastern)
• Vietnam: cây ráng.

• A. caudatum . Slender maidenhair (Am)
• Indonesia: suplir berekor
• Philippines: alambrilong, gubat
• Thailand: hang nak bok, tin tukkae (central), kut namkhao (northern)
• Vietnam: cây rớ den.

• A. flabellulatum
• Indonesia: paku angin-angin
• Vietnam: cây vót, tóc vệ nữ.

• A. philippense
• Indonesia: kamuding
• Malaysia: paku sisek, paku mega
• Philippines: kaikai, kulantrillo, palsik
• Thailand: hang chingcha (peninsular), kut hu khwak, hua khwak (south-eastern).

Origin and geographic distribution

The most primitive representatives of Adiantum occur in the Old World tropics but most species are present in the American tropics. It is distributed pantropically with extensions to the subtropics and even temperate regions. The total number of species is disputed, but is in the range of 150-200. In South-East Asia 10-20 species are present. A. capillus-veneris is found all over the world in warm temperate and subtropical climates; in the tropics it is less common but is often found cultivated as an ornamental. A. caudatum is widely distributed in the Old World tropics from Sri Lanka throughout tropical Asia to the Pacific islands. A. flabellulatum occurs from India and southern China throughout South-East Asia to Taiwan and southern Japan. A. philippense is distributed throughout the tropics from the Old World. Many Adiantum species, including the major species mentioned here, are also widely cultivated as indoor and outdoor ornamentals.

Uses

The beautiful habit of Adiantum species makes them attractive for indoor (cool climates) and outdoor (warm climates) decorative ornamentals; A. caudatum and A. philippense particularly are also used in hanging baskets or pots. Most species are also used medicinally. In many European pharmacopoeias the rhizome and leaves of A. capillus-veneris are considered antiparasitic, antitussive, expectorant, demulcent, febrifuge, haemostatic, refrigerant, tonic and mildly astringent, and infusions or syrups are recommended in chest disorders, bronchitis, nasal catarrh, laryngitis and to aid detoxification for alcoholics. In Colombia it is used as diaphoretic and emollient as well as for problems of the urinary tract. Externally, it is applied to alleviate insect stings and snake bites. An infusion serves as shampoo against dandruff and other skin problems and is said to promote hair growth. Very young shoots, when still tightly coiled, are eaten as a vegetable. The petioles and rachises of the leaves are sometimes used to make baskets. In South-East Asia A. caudatum and A. philippense have the same medicinal uses as A. capillus-veneris in Europe and a number of Adiantum species are used likewise in South America. In the Philippines, the leaves of A. caudatum are also used internally against diabetes, cough and fever. Pounded leaves of A. philippense are applied for poulticing swellings, whereas a decoction is used to alleviate stomach-ache, colic, dysentry and is considered to be a uterine tonic after childbirth.

Production and international trade

Maidenhair ferns are commonly cultivated commercially and non-commercially all over the world. Trade in northern America, Europe and Australia is believed to reach impressive quantities, but statistics are lacking. In South-East Asia production and trade are on a much smaller scale, mostly locally, both for medicinal and ornamental uses.

Properties

In general the Old World species of Adiantum are richer in proanthocyanins, simple flavonoids and simple cinnamic acid esters when compared to New World species, which might mean that the New World species are more advanced. A. capillus-veneris has an aromatic lily fragrance; some of its constituents (present in all parts) include filicine, filicinal, fernene, β-sitosterol, stigmasterol, gallic acid, capillarine (bitter principle), terpenoids (adiantone), flavonoids (kaempferol, rutin, quercetin), cinnamic esters, amygdalin, saponin, mucilage and tannin. In Europe, the use of Adiantum as a drug has been well known since antiquity. It is used to treat various illnesses of the respiratory tract and is taken in the form of tea (infusion) or syrup (extract). Because of the similarity of the glossy blackish petiole and rachis to pubic hair, the drug was used to promote pubic hair growth and dark hair colour. There are reports of dried maidenhair (used as a herbal medicine) being made impure by the addition of leaves of Pteridium aquilinum (L.) Kuhn. Extracts of A. capillus-veneris show antimicrobial activity at a concentration of 2 mg/ml against Bacillus subtilis , Candida albicans , Candida pseudotropicalis (synonym: Candida kefyr ) , Escherichia coli, Proteus vulgaris , Pseudomonas aeruginosa and Staphylococcus aureus . In A. capillus-veneris a volatile oil is present of which both aqueous and alcoholic extracts of 0.02 mg/ml inhibited the growth of Aspergillus flavus, Aspergillus niger, Aspergillus fumigatus, Bacillus subtilis, Corynebacterium ovis, Streptococcus pyogenes and Trichophyton mentagrophytes . Wounds created surgically in the thigh of guinea pigs and infected with Streptococcus pyogenes healed in 10-14 days when treated with aqueous or alcoholic extracts of the oil; healing took 8 days when the wound was treated with terramycin. The inhibitory effect of the extracts is directly proportional to the concentration of the applied oil. A hypoglycaemic activity of the extract was demonstrated to improve glucose tolerance. The aqueous extract of an unspecified Adiantum species significantly inhibited aflatoxin production by Aspergillus parasiticus on agricultural commodities such as rice, wheat, maize and groundnuts. Extracts of A. caudatum reduced growth and germination of Alternaria brassicicola and Aspergillus niger . Rhizome extracts were more toxic than leaf extracts. Two triterpenoid constituents of A. monochlamys Eaton, neohop-12-ene and adiantane, greatly inhibited Epstein-Barr virus activation induced by the tumour promoter TPA.

Description

Terrestrial (rupestral) ferns with shiny black rachises and flabellate ultimate segments. Rhizome creeping to erect, scaly. Leaves monomorphic or nearly so; petiole usually adaxially sulcate, not jointed to the rachis; lamina very variable, simple to pinnately decompound, leaflets dimidiate (half subcircular) or flabellate, herbaceous to papyraceous, glabrous or hirsute, veins usually free. Sori along veins on inner face of reflexed marginal flaps (which thus serve as indusia and also bear the sporangia); annulus of 13-30 thickened cells. Spores trilete, smooth, tetrahedral-globose and with prominent angles, 25-50 μm in diameter.

• A. capillus-veneris. Rhizome short, creeping, densely covered with narrow scales 3 mm long, brown. Petiole 3-8 cm long, lustrous blackish-purple as is the rachis; lamina bipinnate, in outline oblong-subdeltoid, 5-20 cm × 3-5 cm, with an apical leaflet, 3-4 pairs of lobed upper pinnae and usually 2-4 pairs of basal pinnate pinnae; basal pinnate pinnae 3-4 cm long, also with a terminal and 1-4 pairs of smaller, sometimes fan-shaped, stalked pinnules; lobed upper pinnae petiolate, subquadrangular, up to 1.5 cm × 1 cm, basal margins meeting at about a right angle, distal margin lobed up to halfway into 4 or 5 lobes which again are shallowly lobed; veins dichotomous, distinct, transparent but basal ones blackish. Sori round or a little elongate, occupying less than the full width of the lobe.

• A. caudatum . Rhizome short, erect, scaly, bearing a dense tuft of leaves; scales sublinear, 4-5 mm long, brown with pale edges. Petiole 4-15 cm long, glossy purplish-black, densely covered with stiff, spreading, dark reddish hairs; lamina simply pinnate, linear-lanceolate in outline, 10-35 cm × 2-4 cm, apex without pinnae and long flagellate (flagellum may start rooting), usually densely hairy, middle pinnae largest, lower ones usually slightly smaller, upper ones gradually becoming much smaller; pinnae subsessile, parallelogram-shaped, up to 2 cm × 1 cm, distal and lateral margins deeply lobed, lobes lobed again; veins conspicuous on the upper surface, radiating from the very short stalk. Sori on the apices of the lobes, the reflexed flaps almost circular or somewhat elongate, hairy.

• A. flabellulatum . Rhizome short, erect or ascending (rarely creeping), scaly, bearing a dense tuft of leaves; scales sublinear, about 8 mm long, shiny yellow-brown. Petiole 10-30(-50) cm long, blackish; lamina pedate or tripinnate with a few pairs of bipinnate pinnae, in outline up to 20 cm × 25 cm; upper pinnae and pinnules of the large pinnae similar, pinnate with more than 10 pairs of leaflets, linear, about 10 cm × 2 cm; leaflets fan-shaped, distinctly stalked, 2 basal margins forming a broad cuneate base, up to 15 mm × 13 mm, distal margin round, serrate, glabrous, veins not raised; fertile leaflets usually not longer than 1 cm. Sori round to elongate, up to 5 mm long.

• A. philippense . Rhizome short, suberect, scaly at the apex; scales sublinear, up to 3 mm long, brownish-black. Petiole up to 10(-25) cm long, bright brown to black; lamina simply pinnate, in outline 15-30 cm × 10 cm, usually bearing 8-15 alternate pinnae and an abnormal terminal leaflet or with prolonged, leafless rachis that may start rooting at the tip when in contact with soil; stalks of pinnae up to 2 cm long; leaflets crescent-shaped, 1-5 cm × 0.5-1.5 cm, base subcuneate, outer margin an almost even curve, entire, crispate or lobed, thin, glabrous, veins fine and slightly raised, many times forked. Sori with reflexed, elongate soral flaps 5-8(-15) mm long; sporangia small, annulus about 18 thickened cells. Spores tetrahedral.

Growth and development

About 3 months after sowing, the spores of Adiantum germinate into prothalli. The gametophyte is cordate, symmetrical, with a thickened central cushion and thin borders. Antheridia are mostly in the basal region among rhizoids, the archegonia more apical on the thickened portion. After fertilization, young sporophytes develop in 4-6 months and the fern fully grown by about 12 months. After 2-3 years the fern starts producing spores.

Other botanical information

Adiantum ferns are easily recognized by the dark polished petioles, the absence of a conspicuous midvein on the leaflets or segments and the false indusium formed by a fold of the leaf margin bearing the sporangia on its underside. Adiantum is an old and morphologically isolated genus. It has been variously classified, e.g. in Adiantaceae (Holttum and many authors), Parkeriaceae (Flora of Thailand), Polypodiaceae (Fern flora of Java), Pteridaceae (Kubitzki, followed here). In the Pteridaceae , it is classified in the subfamily Adiantoideae with Adiantum as the only genus. Within the genus various groupings have been proposed (based on anatomy, morphology, and chemistry), but a thorough, up-to-date, worldwide revision, incorporating all findings, is missing.

• A. capillus-veneris . Because of its wide distribution, numerous forms have developed, with variations in leaf form, size and even chemical content. Many cultivars have been distinguished for ornamental use, particularly in the United States and Great Britain. Some well-known cultivars are: "Fimbriatum", Imbricatum", "Magnificum", "Mairisii" and "Scintilla". The North American A. pedatum L. is often used as a substitute for its medicinal uses.

• A. caudatum . This species is for tropical South-East Asia what A. capillus-veneris is for the non-tropics. In the past A. caudatum was considered a very variable species; variations were sometimes distinguished as varieties and cultivars were developed for ornamental use. In a narrower species concept, the A. caudatum complex is subdivided into 4 species, which can be distinguished as follows (the distribution and ecological requirements are similar for all):

• A. caudatum : pinnae sessile, rachis hairy, pinnae hairy, lobed more than halfway towards the costa; veins prominent with white setose hairs; indusial flaps almost circular;

• A. zollingeri Mett. ex Kuhn (synonym: A. caudatum var. subglabrum Holttum): pinnae sessile, rachis hairy, pinnae glabrous, lobed less than halfway towards the costa; veins not prominent, brown hairy; indusial flaps broader than long;

• A. edgeworthii Hook. (synonym: A. caudatum var. edgeworthii (Hook.) Bedd.): pinnae sessile with completely glabrous rachis;

• A. soboliferum Wall. ex Hook. (synonym: A. caudatum var. soboliferum Bedd.): pinnae stalked, glabrous, crescent-shaped, longer than 2 cm, petiole and rachis distinctly winged.

• A. flabellulatum . It is closely related to the more common South-East Asian A. stenochlamys Bak. which has distinctly pinnate leaves with more widely spaced leaflets that are almost symmetrical.

• A. philippense. Owing to its wide range this species is very variable; in deep shade leaflets become larger and thinner, in exposed situations plants can become dwarfed. It is closely related to A. soboliferum , which has a distinctly winged petiole and rachis. Specimens from China (2 n = 60) have (16) 32 spores in each sporangium instead of the usual 64 and may be agamosporous diploids.

A. tenerum Swartz (brittle maidenhair) is one of the non-indigenous Adiantum species most commonly cultivated (that often escapes) in South-East Asia as an ornamental with numerous attractive cultivars. In tropical America, where it originates, it is also used medicinally.

In the American continent A. raddianum Presl is the most important ornamental species of which numerous cultivars have been developed. In India, China and Nepal A. venustum D. Don is an important ornamental.

Ecology

All maidenhair ferns prefer light shade and ample moisture. A. capillus-veneris prefers a subtropical and warm temperate climate and often grows near streams in spray and in light shade at low altitudes. It is not well suited for perhumid tropical climates, where it can survive in exposed but moist locations on walls but where it does not reproduce freely. It can survive temperatures as low as -2°C, but growth is then completely seasonal. Of the cultivated species A. capillus-veneris is perhaps the most adaptable, with cultivars for different ecological circumstances. A. caudatum is most suited to drier and more seasonal climates, on well-drained soils such as limestone, from sea-level up to 1200 m altitude. The pinnae are sometimes deciduous and in very dry conditions the leaves curl up. A. flabellulatum prefers humus-rich soils in rather open forest up to 1500 m altitude. A. philippense grows in almost the same habitat as A. caudatum , but is more delicate. It grows from sea-level up to 1000(-1400) m on rather dry slopes or on muddy crevices of rocks in light shade or sometimes on the humus-rich floor of dense montane forest. Aboveground parts disappear in the dry months.

Propagation and planting

Adiantum can be propagated by spores, rhizome parts and clump division. When sowing spores, the planting medium and container should be sterilized before use. Moist fine compost or sphagnum alternated with layers of wet crushed brick or gravel are suitable. The container is covered with glass or polythene sheeting, kept in the shade with a temperature between 18-24°C, and regularly sprayed with water. Often evaporation from the container itself is sufficient for germination. After 3 months the container will have become very crowded with prothalli. The prothalli should be moved to another container with the same medium at a spacing of about 2.5 cm. After 4-6 months young ferns will be 5-10 cm tall and should be transplanted to another container. By 10-12 months the ferns are fully developed. Propagation by clump division is easier and faster. The clump is taken out of the container, cut with a sharp knife and the new sections can be grown as separate plants. Adiantum grows well on soils rich in organic matter, such as peat moss or leaf mould mixed with coarse sand or loam, with pH 6.5-7.

Husbandry

Adiantum grows well on sites free from wind and drying drafts since the foliage is easily desiccated or damaged by air movement. A relative humidity of 50-80% is preferred. A fine spray or mist of water applied on warm dry days will help to protect the leaves against burning but good drainage is important as Adiantum ferns do not withstand waterlogging. Regular fertilizer application is recommended (for example every 2-3 weeks with a balanced NPK mixture). Old leaves should be removed regularly to provide space for new ones and to allow some light to penetrate the inner part of the clump. During winter or the resting season all leaves can be cut back and the plants enter a resting period until the new growing season.

Diseases and pests

Adiantum is particularly susceptible to attacks by snails, slugs, pill bugs and sow bugs. Persistent use of baits and poisons offers protection.

Harvesting

For ornamental use, Adiantum plants grown from spores can be traded about one year after sowing. Plant parts are harvested in the growing season whenever needed for medicinal uses.

Handling after harvest

For medicinal use harvested leaves and rhizomes of Adiantum can be dried and stored.

Genetic resources and breeding

There are no known germplasm collections of Adiantum , but commercial growers keep their stock of cultivars and various interesting forms. Some breeding for improved ornamental cultivars is carried out in the United States.

Prospects

Adiantum is a popular ornamental all over the world. It is worthwhile investigating the possibilities for large-scale cultivation of locally available species and cultivars in South-East Asia. The medicinal properties of the South-East Asian Adiantum need further research.

Literature

• Backer, C.A. & Posthumus, O., 1939. Varenflora voor Java [Fern flora for Java]. 's Lands Plantentuin, Buitenzorg, Dutch East Indies. pp. 164-170.
• Cooper-Driver, G. & Swain, T., 1977. Phenolic chemotaxonomy and phytogeography of Adiantum. Botanical Journal of the Linnean Society 74: 1-21.
• Holttum, R.E., 1966. A revised flora of Malaya. 2nd Edition. Vol. 2. Ferns of Malaya. Government Printing Office, Singapore. pp. 596-604, 638.
• Hoshizaki, B.J., 1970. The genus Adiantum in cultivation (Polypodiaceae). Baileya 17: 97-191.
• Mahran, G.H., El Alfy, T.M., Taha, K.F. & El Tantawy, M., 1990. Chemical composition and antimicrobial activity of the volatile oil and extracts of leaves of Adiantum capillus-veneris L. Bulletin of Faculty of Agriculture, University of Cairo 41: 555-572.
• Tagawa, M. & Iwatsuki, K., 1985. Adiantum. In: 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. 206-216.
• Tryon, R.M., 1990. Pteridaceae, subfamily Adiantoideae. 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. 247-249.
• 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. 56-60, 169-179.

Authors

J.J. Afriastini