Wikstroemia Endl. (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Wikstroemia Endl.

Protologue: Prod. fl. Norfolk.: 47 (1833) (" Wickstroemia ").

Family: Thymelaeaceae

Chromosome number: x= 9;W. indica: 2n= 27 (apomictic triploid), 28, 36, 52

• Wikstroemia indica (L.) C.A. Meyer, Bull. Phys.-Math. Acad. Imp. Sci. St. Petersb. 1: 357 (1843), synonyms: Daphne indica L. (1753), Wikstroemia viridiflora Wallich ex Meisner (1841), W. linearifolia Elmer (1910).

• Wikstroemia lanceolata Merrill, Govt. Lab. Publ. (Philip.) 29: 31 (1905), synonym: W. angustissima Merrill (1912).

• Wikstroemia meyeniana Warb., in Perkins, Fragm. fl. Philip.: 171 (1905), synonyms: Daphne cannabina auct. non Lour., Schauer (1843), Wikstroemia longifolia Lecomte (1915), W. fenicis Merrill (1918).

• Wikstroemia ovata C.A. Meyer, Bull. Phys.-Math. Acad. Imp. Sci. St. Petersb. 1: 357 (1843), synonyms: Daphne indica Blanco (1837), D. foetida Blanco (1837).

• General: salago (En)
• Philippines: salago (Tagalog, Bisaya, Bikol).

• W. indica : small-leaf salago, tiebush (En)
• Indonesia: perapata, posi-posi (Sulawesi)
• Philippines: arandon (Ilokano), inyam (Panay Bisaya), salagong-liitan (Tagalog)
• Vietnam: (cây) gió, gió móc, gió miệt.

• W. lanceolata : lance-leaf salago (En)
• Philippines: karanpinig (Negros), salagong-sibat (Tagalog), tuka (Ilokano).

• W. meyeniana : large-leaf salago (En)
• Philippines: sagu (Tagalog)
• Vietnam: (cây) tóc, gió miềt, gió quê.

• W. ovata : round-leaf salago, oval-leaf salago (En). Brunei Darussalam: gelam hutan
• Malaysia: pait-pait (Sabah)
• Philippines: arandon (Ilokano), dapnit, suka (Bontoc).

Wikstroemia comprises about 70 species and is widely distributed from East Asia at about 37N southward through South-East Asia to Australia and across the Pacific to Hawaii. W. indica is widely distributed from India and Sri Lanka through South-East Asia to China and Taiwan, and to Australia, Fiji and the Cook Islands. In South-East Asia it occurs naturally in Thailand, Indo-China, Malaysia and the Philippines, whereas in Java (Indonesia) it has naturalized widely around the Botanical Gardens in Bogor and near Cipanas on Gunung Gede. W. lanceolata occurs in the Philippines (Palawan, Mindoro and Luzon) and Taiwan. W. meyeniana is found in Thailand, Cambodia, Vietnam and the Philippines. W. ovata grows in Borneo and throughout the Philippines.

The inner bark of various Wikstroemia spp. yields a fibre which is an excellent raw material in the manufacture of high grade paper requiring strength and durability, such as paper currency, cheques and legal documents. It is also suitable for handmade paper. In mixtures with other fibres it can be used for paper of lesser quality. Salago fibre is also made into strong ropes and strings, e.g. in the Philippines and Vietnam. Other applications in the Philippines include fishing lines and nets, clotheslines, sacks, textile fabrics, mosquito nets, bags, wallets and hats. Applications elsewhere are in the production of Japanese sliding doors ("shoji"), kimonos and components for radios and microcomputers.

W. indica is used as firewood in Indo-China, where root decoctions are used to provoke vomiting in case of poisoning and crushed leaves are applied to treat furunculosis and phlegm. However, as the plants are rather poisonous, care should be taken when any part is used internally. In the Philippines, root decoctions of W. lanceolata are taken to treat amoebic dysentery, whereas W. ovata leaves are chewed and swallowed as a purgative, filings of the bark in water or wine are taken as a tonic, and fresh bark or branches are tied around the neck to relieve bronchial catarrh. Ground or pounded salago roots, leaves and stems are placed in porous containers to stupefy and catch fish.

In the Philippines salago is mainly harvested from the wild, the most commonly collected species being W. indica and W. lanceolata , but it is also grown commercially. Commercial production is mainly concentrated in Central Visayas. The annual quantity of baled salago fibre in the Philippines in 1990-1999 ranged from 800-950 t, of which 700-910 t came from Central Visayas. Annual exports of salago fibre in the same period ranged from 590-830 t, the countries of destination being China, Japan, South Korea, Taiwan and Thailand. Salago pulp was exported to Taiwan in 1998 (5 t) and 1999 (20 t). Most domestic consumption is by local producers of handmade paper. No statistics are available on salago production and trade in other countries.

Wikstroemia bark yields a light-coloured, long, supple and strong bast fibre with a silky appearance. The ultimate fibre cells of W. ovata in the Philippines have been found to be (1.6-)2.9(-4.2) mm long, with a diameter of (3-)12(-21) μm, a lumen diameter of (1-)2(-4) μm and a cell wall thickness of 1-10 μm. In a comparative study in the Philippines, handsheets with a basic weight of 65 gsm made from Wikstroemia pulp (beaten to a freeness of 150-230 mL) had a tear index of 16.8 mN.m²/g, a tensile index of 101 N.m/g and a folding endurance of 619. They were slightly inferior to handsheets made from abaca ( Musa textilis Née) (18.5 mN.m²/g, 106 N.m/g and 2127), but superior to those made from rice ( Oryza sativa L.) straw and Acacia mangium Willd. wood (3.7 and 6.9 mN.m²/g, 25 and 40 N.m/g, and 7 and 10, respectively).

All parts of W. indica are poisonous but fruits are more toxic than leaves and children have died from eating the fruits. The toxins are coumarin-like compounds which may cause internal haemorrhage and death to livestock. The dicoumarin daphnoretin, isolated from the stems of W. indica , has shown in vivo anti-tumour properties against Ehrlich ascites carcinoma in mice. Daphnoretin is a protein kinase C activator with suppressive effects on hepatitis B virus gene expression in human hepatoma cells and inducing respiratory burst. Tricin, kaempferol-3-O-β-D-glucopyranoside and (+)-nortrachelogenin (wikstromol) isolated from W. indica stems have antileukaemic properties. The lignan (+)-nortrachelogenin also has effects on the central nervous system, producing depression in rabbits. Daphnoretin, (+)-nortrachelogenin, genkwanol A, wikstrol A, wikstrol B and daphnodorin B isolated from W. indica roots showed antifungal activity, whereas (+)-nortrachelogenin, genkwanol A, wikstrol B and daphnodorin B were moderately active against human immunodeficiency virus type 1 (HIV-1) in vitro. Genkwanol A, wikstrol A and B and daphnodorin B showed moderate antimitotic activity. Wikstromin, a flavone glycoside isolated from the root bark of W. indica , showed diuretic action when intravenously injected in anaesthetized dogs. Despite the presence of anticarcinogenic compounds and reported anticancer activity of plant extracts, W. indica has also shown cancer-promoting effects in mice and rats and an activating effect on the Epstein-Barr virus.

As a raw material for currency paper and other specialty paper, Wikstroemia mainly has to compete with abaca, the dominant source, and hemp ( Cannabis sativa L.).

Evergreen or deciduous shrubs or small trees. Leaves opposite or in whorls of 3, variable in texture and shape. Inflorescence terminal or axillary, in fascicles or solitary, arranged in or resembling a spike, raceme, umbel or head; flowers subsessile or with articulated pedicel, 4-merous, bisexual; floral tube corolla-like, usually with 4 spreading lobes; stamens 8, sessile or with filaments, in 2 distinct groups (inserted in tube, 4 upper, 4 lower), anthers basifixed; disk cup-shaped, deeply lobed or free and scale-like, crenate or dentate; pistil sessile, with 1-celled ovary, a short style and large subglobose stigma. Fruit drupaceous, pericarp fleshy or membranous, 1-seeded. Seed of same shape as fruit, black.

• W. indica . A shrub, up to 3 m tall, often dichotomously branched with black-brown branchlets, sometimes transversely fissured, scattered puberulous when young. Leaves subopposite, subcoriaceous, obovate to elliptic-oblong, 1-7 cm × 0.5-3 cm, shiny above. Inflorescence a 3-7-flowered raceme, subsessile, 3-6 mm long; pedicel up to 2 mm long, articulated below the middle; flowers about 1 cm long, green-yellow, lobes 2-3 mm long; stamens with very short filament, the 2 groups about 1 mm apart; disk consisting of 2 free linear scales 0.8 mm long; ovary 2 mm, style less than 0.5 mm long. Fruit ovoidal to broadly ellipsoidal, about 6 mm × 4 mm, red, sometimes at base surrounded by remnants of floral tube. Seed 3.5-5.5 mm long, black.

• W. lanceolata . A shrub, up to 4 m tall, young branches densely appressed pubescent. Leaves opposite, papery, lanceolate, 3-9 cm × 0.5-2.5 cm. Inflorescence umbelliform to shortly spicate, terminal, usually 3-5-flowered (rarely up to 20); peduncle 0-15 mm long, pedicel 1-1.5 mm, articulated at the middle or in upper half; flowers yellow-green, 6-15 mm long, lobes 1 mm long; disk consisting of 2 free linear scales. Fruit ovoidal, about 8 mm × 5 mm, red. Seed 6 mm long.

• W. meyeniana . A shrub, 1-3 m tall with sparsely pubescent to glabrous young branches. Leaves opposite, papery, oblong to lanceolate, 5-13 cm × 2-5 cm. Inflorescence umbelliform, 5-6(-10)-flowered; peduncle up to 3 cm, pedicel 1-2 mm long; flowers green-yellow, about 2 cm long, densely puberulous outside, lobes 2-3 mm long; stamens sessile or filament up to 0.5 mm long; disk consisting of 2 free oblong scales; ovary obovoidal, 2 mm long, style distinct, up to 1 mm long, stigma up to 0.5 mm in diameter. Fruit ovoidal, about 8 mm × 6 mm, red, surrounded at base by remnants of floral tube.

• W. ovata . A shrub, up to 5 m tall with glabrous to appressed-hirtellous branchlets. Leaves opposite, papery, ovate to oblong, 4-14 cm × 3-5 cm. Inflorescence terminal, short spicate or umbelliform, 7-20-flowered; pedicel articulated near the apex; flowers 1-2 cm long, green-yellow, lobes 2-4 mm long; disk consisting of 2 free oblong scales; ovary ellipsoidal, 2-3 mm long, style about 1 mm long, stigma capitate. Fruit subglobose to ellipsoidal, 8-10 mm × 6-8 mm.

Wikstroemia seed usually germinates 7-15 days after sowing. The seedling grows slowly. In the Philippines plant height increases of 3-17 cm per month have been recorded in the first year after planting. Fruits are produced 6-9 months after planting and 30-35 days after flowering. The fruits ripen in about 20 days. Wikstroemia is probably insect-pollinated and the fruits are dispersed by birds or other animals. In Java W. indica flowers year-round. In Indo-China W . meyeniana flowers year-round and fruits from August to December. Apomixis has been found in W. indica . After cutting Wikstroemia new shoots will develop from the stump.

Within the Thymelaeaceae , Wikstroemia belongs to the subfamily Thymelaeoideae together with, among others, the fibre-yielding genera Daphne L., Enkleia Griff. and Phaleria Jack. In view of the minor differences between Wikstroemia and Daphne it has been suggested that the two be combined into a single genus, Daphne . All Malesian Wikstroemia species belong to the subgenus Wikstroemia . Specific delimitation in Malesian Wikstroemia is difficult. W. indica is highly variable in its vegetative parts but no well-defined infraspecific taxa can be distinguished.

The bark of W. poilanei Léandri is used for making cordage in Vietnam, whereas its root is credited with purgative properties. W. ridleyi Gamble is used in traditional medicine in Peninsular Malaysia: the pounded bark is applied to boils, and the leaves are considered aperient.

Wikstroemia occurs in primary and secondary forest at low and medium elevations, along roads and river banks, on marginal land, in coconut plantations and pasture land. Though it can grow in a range of rainfall conditions and in many soil types, the highest production is obtained on fertile, well-drained soils. W. indica grows in thickets and secondary vegetation, usually up to about 1300 m altitude, but sometimes as high as 2700 m altitude, for instance in Sulawesi (Indonesia) and New Guinea. It tolerates many soil types and occurs in various habitats, such as on sandy soils along the seashore, on limestone ridge tops, on granite peaks, along river banks and on open hillsides. W. lanceolata is commonly found on forested slopes up to 1300 m altitude. It is probably a short-day plant and it tolerates partial shading. W. meyeniana can be found over a wide range of ecological conditions, e.g. in humid primary forest, degraded formations and forest edges, and on many soil types, up to 1500 m altitude. W. ovata is found in thickets, primary and secondary forest up to 800 m altitude.

Wikstroemia is normally propagated by seed, but vegetative propagation by stem cuttings is also possible. Ripe fruits are collected, macerated, and the seeds are separated from the pulp by hand, rinsed and then dried. Dried seeds can be stored temporarily or planted directly. In a Philippine study the germination percentage of seed stored for 5 months under ambient (27-30°C) and refrigerated (10-15°C) conditions was 40-50% and 80%, respectively. Planting is usually in a nursery in seedplots or in seedboxes containing 50% sand and 50% top soil. After germination the seedlings may be thinned out to a lower density and transplanted from seedboxes into plastic bags. Plants at least 20 cm tall can be planted out in the field 2-4 months later. The best time to plant salago in the field is at the start of the rainy season. The planting site should be cleared, all weeds removed and planting holes (20 cm × 20 cm × 20 cm) made 1 m × 1 m apart.

In vitro micropropagation of salago is possible. Node explants cultured in pure Murashige and Skoog (MS) medium formed leaves, and upon subculturing in MS medium with 0.5 or 1.0 g benzyladenine (BA) and 0.5 or 1.0 g naphthalene acetic acid (NAA) the node explants formed normally growing shoots.

Weeding of Wikstroemia is necessary during early plant growth and dead seedlings may be replaced to maintain the plant density. No fertilizer recommendations are known to exist. Lateral sprouts develop one month after stem harvesting. Only 3-4 sprouts are maintained on small stumps while 5-7 sprouts are left in bigger stumps.

The most common and destructive disease of Wikstroemia in the Philippines is stem rot caused by the fungus Botryodiplodia theobromae , which attacks all four Wikstroemia species treated here. It is characterized by wilting and drying of the leaves, followed by browning and drying of the stem and defoliation. The plant dies if the basal part of the stem is infected. Fungicides can protect plants from infection but cannot completely arrest the disease. Sanitation measures such as the removal and burning of diseased plant parts are recommended to limit the damage.

Aphids, locusts, mirid bugs, grasshoppers and mites attack salago plants and may be controlled using insecticides.

For wild Wikstroemia plants, cutting depends on plant height and stem diameter. Salago gatherers in the Philippines usually fell the plant and strip off the bark with a knife, but sometimes the bark is stripped from unfelled plants. The bark is usually sold unprocessed to middlemen or buyers. Cultivated salago can be harvested 2 years after planting and the regrowth every 2 years thereafter. Cutting stems one month before the start of the rainy season has been recommended to ensure that the salago stumps survive and produce new shoots. The stems are cut diagonally 3-4 cm above ground level, after which all branches are removed. The stem and all branches with a diameter of at least 1 cm are cut into pieces 45 cm long and bundled together. Branches with a smaller diameter are used for other purposes, such as firewood.

In the Philippines Wikstroemia reportedly yields up to 4-5 t/ha dry fibre at the first harvest with slightly higher yields at subsequent harvests, but these figures seem too high when compared to the yield of other perennial bast fibre crops, such as Abroma augusta (L.) L.f. and Broussonetia papyrifera (L.) L'Hér. ex Vent.

Wikstroemia fibre is extracted either by the so-called "hand-cleaned" (or "direct") method or by the "steam" (or "boiling") method. The hand-cleaned method consists of directly peeling the bark off the stem, scraping the outer bark from the fibre and drying the fibre in the sun. In the steam method the stems and branches are steamed for about 2 hours in a container, without the stems touching the water, as this stains the fibre. After steaming the outer bark is removed from the stem by firmly gripping the stem with jute or plastic sacks in one hand and sliding it through the palm of the other hand. The fibre is then removed from the stem by scraping after which it is dried in the sun and bundled. The steam method is usually preferred because the fibre recovery is higher and the fibres can be stored for a longer time. The hand-cleaned method produces a white fibre which is susceptible to moulds and therefore cannot be stored for a long period. In the Philippines a grading system for salago fibre is available, consisting of 4 classes of hand-cleaned salago: SG-1 (salago superior), SG-2 (salago good), SG-3 (salago fair), SG-X (salago residual); and 4 classes of steamed salago: S-SG-1 (steamed salago superior), S-SG-2 (steamed salago good), S-SG-3 (steamed salago fair), S-SG-X (steamed salago residual). The exports of salago fibre from the Philippines in 1990-1999 mainly consisted of salago grade S-SG-3.

No germplasm collections or breeding programmes of Wikstroemia are known to exist.

Salago fibre remains in high demand in international markets, especially in Taiwan, Korea and Japan, which gives good prospects for Wikstroemia cultivation and fibre production in South-East Asia. To develop the salago industry, improved methods of bark harvesting, drying and storage should be promoted as well as better management techniques. New plantations must also be established because natural Wikstroemia populations have decreased due to continuous harvesting. In the Philippines support to the salago industry is provided by the Fiber Development Authority (FIDA) which conducts research to improve cultivation, processing and marketing. As well as good-quality fibre, Wikstroemia contains compounds that may have potential in drug manufacture. Pharmacological research has shown very interesting activities, such as antitumour, anti-HIV and antifungal properties, that deserve more attention.

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N.O. Aguilar, P.M. Po, C.S. Tawan & B.E. Umali