6527

17: Fibre plants

Broussonetia papyrifera (L.) L'Hér. ex Vent.

Tabl. règn. vég. 3: 547 (1799).

MORACEAE

2n = 26

Morus papyrifera L. (1753), Smithiodendron artocarpioideum Hu (1936), Broussonetia papyrifera (L.) L'Hér. ex Vent. var. sumatrana (Miq.) Bur. (1873).

Paper mulberry, paper mulberry tree, tapa-cloth-tree (En). Mûrier à papier (Fr). Indonesia: saeh (Sundanese), galugu (Javanese), dhalubang (Madurese). Burma (Myanmar): malaing, thale, dalaing. Cambodia: rong. Laos: po sa (Vientiane), sa lè (Xieng Kouang), may sa. Thailand: po krasa (central, northern), momee (central), po faai (peninsular). Vietnam: (c[aa]y) d[uw][ows]ng, ch[uwr], ch[uwr] d[af]o ph[uj].

The natural range of distribution of paper mulberry comprises Japan, China, Indo-China, Thailand, Burma (Myanmar) and India (Assam). It has been introduced into the Ryukyu Islands, Taiwan, the Philippines, Indonesia (Sumatra, Java, Sulawesi, the Lesser Sunda Islands (Flores, Timor, Alor and Wetar) and the Moluccas), New Guinea and Polynesia. It is found in the collections of many botanical gardens in subtropical and temperate regions. It is naturalized in some areas, for instance southern Europe and the southern United States. It has been cultivated in East Asia, Indonesia and Polynesia since early times.

For centuries the tough and interlacing bast fibre from the inner bark of paper mulberry has been used to make paper and textile fabric for clothing. The former application is found in Japan, China, Indo-China, Thailand, Burma (Myanmar), the Philippines, Java and Madura, although with different production methods, and the latter in, among others, Indonesia, New Guinea and Polynesia, where the fabric is known as 'tapa' cloth. Around 100 AD paper mulberry fibre was made into a form of paper in China, although the sheets made were not paper in the usual sense. They consisted of strips cemented together instead of liberated fibres deposited randomly. Around 600 AD paper manufacturing from paper mulberry reached Japan, where a high-quality paper industry became established. In general, paper mulberry paper made in Japan, mainland China and Taiwan is of higher quality than that made elsewhere, e.g. in (northern) Thailand and Indonesia. The very strong paper made of paper mulberry bast fibre in Japan is used for writing and the construction of lanterns and umbrellas, whereas paper made in Thailand often serves for wrapping, e.g. the Shan people used it to wrap raw opium. Both the bark and the wood can be used for paper pulp production, making it possible to utilize the whole stem. Textile fabric from paper mulberry is used to make items such as sarongs, head-cloths, bed clothing and bags. The fibres are sometimes made into rope or cord, e.g. in Indonesia. The Lahu people in northern Thailand also use the roots for this purpose.
In Indonesia the steamed young leaves are eaten as 'lalab'. The sweetish infructescences ('fruits') are edible as well. The leaves are fed to pigs in Indo-China and to silkworms in China. In Indo-China the leaf of paper mulberry is considered a laxative for children and a diaphoretic, and the fruit a pectoral, stomachic and tonic, whereas the bark is taken against dysentery and haemorrhage and the latex applied externally against snake- and dog bites and bee stings.

In South-East Asia paper mulberry fibres are mainly used locally, and paper making is usually a home industry. In the Philippines handmade paper is produced for domestic use as well as export markets, but production statistics are not available. Research on commercial paper production at the beginning of the 20th Century indicated that the quality of the paper based on raw material from Java (Indonesia) and the production methods applied were too poor to create a suitable market.

Paper mulberry bast fibres are soft, lustrous and very strong. The inner bark is about 2 mm thick and dense and homogeneous because of the minute pith rays. The fibre cells are (6—)10—15(—25) mm long and (12—)25—30(—36) µm wide. Their walls are often thick and their ends are usually pointed or blunt, though other shapes may also occur. Dislocations and cross-markings are frequent but finer than those in flax (Linum usitatissimum L.) and hemp (Cannabis sativa L.) fibre. The bark also contains a second type of fibre cells, which are wide, thin-walled and ribbon-like, with rounded ends. Paper mulberry fibres are often enveloped by a transparent membrane (the loosened primary wall), which distinguishes the fibres of this species from those of many other bast fibre species. Parenchyma with cells containing prismatic calcium oxalate crystals and milksap tubes (lactifers) are also found in the bark. The wood fibres are (0.1—)0.8—1.2(—1.4) mm long and (17—)22—30(—47) µm wide. Oven-dry wood contains 59% cellulose, 23% lignin, 16% pentosans and 1% ash.
The wood and bark of paper mulberry can be pulped, separately or together, with a number of processes, including the mechanical, kraft and APMP (alkaline peroxide mechanical pulping) processes. Pulping experiments with the whole stem for the production of bleached sulphate and rayon grade pulp have been promising. Bast fibre pulp may be used in blends to increase the tear strength of short-fibred pulps. Interaction of resinous substances with inorganic compounds, especially calcium, may cause ink-repellent spots in paper made from paper mulberry bast fibre.
The flavonoid broussochalcone A (a phenylated chalcone), isolated from the bark, is a powerful antioxidant, primarily because of its free radical-scavenging activity, and also suppresses the production of nitric oxide (NO). As excessive free radicals and NO-production have been associated with various inflammatory diseases, broussochalcone A may have therapeutic potential. It is also a potent inhibitor of platelet aggregation and an inhibitor of respiratory burst in neutrophils. Other compounds with activity against platelet aggregation isolated from the bark of paper mulberry are broussoaurone A, broussoflavan A, broussoflavonols F and G and kazinol A and B. Broussoaurone A, broussoflavan A and broussoflavonol F and G also have antioxidant properties. Broussonin A and B from the bark have shown antifungal and antibacterial activity. Other compounds isolated from the bark are broussochalcone B, broussoflavonol A and B, butyrospermol acetate, erythrinasinate and isoprenylated aurone. Broussoflavonol C, D, E and F, papyriflavonol A, lignoceric acid, marmesin, octocosan-l-ol and squalene have been isolated from the root bark.

As many representatives of the order Urticales, for instance Artocarpus spp. and Ficus spp., have fibres suitable for barkcloth and papermaking, they may be substituted for paper mulberry fibre. Hemp (Cannabis sativa L.) and flax (Linum usitatissimum L.) may be used as substitutes for reinforcing short-fibred pulps.

A deciduous, dioecious, suckering tree, up to 12(—35) m tall (in cultivation often a multi-stemmed shrub about 3 m tall), containing milksap, with small, axillary, scaled resting buds and shoot apices that are shed. Trunk gnarled, outer bark smooth, inner bark consisting of tough interlacing fibres that can be extracted in broad layers; leafy twigs 1.5—3 mm thick, subtomentose to hirtellous to puberulous. Leaves alternate and spirally arranged or subopposite; stipules free, semi-amplexicaul, ovate, 0.5—1.5 cm long, puberulous, slightly ribbed, caducous; petiole (1—)2—9(—15) cm long, subtomentose; blade ovate to cordiform or elliptic, 5—20 cm x 4—12 cm, entire or up to 5-lobed, slightly asymmetrical, chartaceous, base cordate to rounded or subcuneate, margin crenate-serrate-dentate, apex acuminate to subacute; upper surface hispidulous, scabrous, lower surface usually densely puberulous to subtomentose on the veins; lateral veins 5—9 pairs, tertiary venation scalariform. Male inflorescences solitary or usually clustered on short shoots, spicate, pendulous; peduncle 1—2.5 cm long, puberulous to tomentellous; spike 3—10 cm long; perianth 4-lobed, 1.5—2 mm long, puberulous; stamens 4, inflexed in the bud and bending outwards elastically, 3—3.5 mm long, anthers about 0.8 mm long; bracts subulate, 1.5—2.5 mm long, puberulous. Female inflorescences capitate, solitary in the leaf axils or below the leaves; peduncle 0.3—1.5 cm long, puberulous to tomentellous; head globose, 1—1.2 cm in diameter; perianth tubular, about 1 mm long, 4-dentate; ovary about 0.5 mm long, stigma 1, filiform, 7—10 mm long; interfloral bracts clavate to subpeltate, 1—1.5 mm long, densely puberulous to tomentellous, the apices cohering, but leaving narrow openings to let the stigmas through. Infructescence a subglobose syncarp, 2—2.5 cm in diameter, its fleshy part consists of the interfloral bracts, which usually turn orange, the perianth remains membranaceous; fruit drupaceous, with a narrow base and white exocarp, the endocarp body ovoid, 2—2.5 mm long. Seed small with curved embryo, flat cotyledons and long radicle.

Paper mulberry is a fast-growing tree, with often abundant sucker formation. Various leaf forms may occur on the same twig: from ovate with entire margins to lobed on one or both sides. In Java (Indonesia) flowering and fruiting is year-round, but trees exploited for their fibres are mostly cut before they reach the flowering stage. Natural reproduction is by seed and root suckers. Paper mulberry trees can regenerate new bark after complete girdling.

Broussonetia L'Hér. ex Vent. comprises 8 species, of which 7 occur in tropical, subtropical and warm temperate regions of Asia, and one in Madagascar. Most Broussonetia spp. are trees and some are or can be climbers. The abscission of the terminal meristem, the elongation of branches by the terminal axillary bud, and the presence of scaled resting buds are features which suggest temperate origins. The same features are found in the genus Morus L. from which Broussonetia differs in the features of the pistillate flowers and inflorescences. Cultivars of paper mulberry include those with laciniate leaf blades, white infructescences, yellow or white variegated leaves, or relatively large leaves.
The closest relative of Broussonetia papyrifera is Broussonetia kazinoki Sieb., mainly from Japan and Korea, whose bark fibre is also used for paper making. In the Philippines it is experimentally grown as a fibre plant. Broussonetia kazinoki also occurs wild in secondary forest in Vietnam, where its roots and leaves are used medicinally against snake bites, pimples, stomach-ache and liver inflammation. Hybrids of Broussonetia papyrifera and Broussonetia kazinoki exist, e.g. in Korea.

Paper mulberry is an element of warm temperate to subtemperate deciduous forest, but it also thrives in tropical lowlands and highlands, in particular in areas with a seasonal climate. It is a vigorous pioneer which can rapidly spread following canopy disturbance or farming and it is sometimes considered a weed, for example in the Philippines. It has been suggested, e.g. in the Philippines, as a potential crop for reforestation and eradication of cogon grass (Imperata cylindrica (L.) Raeuschel).

Paper mulberry is easily propagated by seed or vegetatively by wood or root cuttings, suckers, layering or grafting. Seeds are not very sensitive to light for germination and can germinate in the dark. In Thailand transplanting of suckers 30 cm tall gave better survival than propagation with root cuttings, stem cuttings or seed. In vitro micropropagation of paper mulberry is possible with axillary buds cultured in Murashige and Skoog medium (MS) supplemented with 1.0 mg/l 6-benzylamino purine (BAP) and 0.01 mg/l alpha-naphthaleneacetic acid (NAA).
Paper mulberry is mostly grown in or near villages.

Paper mulberry is easy to cultivate, needing no special care. In Indonesia, lateral branches are sometimes pruned and the stem may be supported. It coppices well, and in Japan it is often cultivated in a coppice cycle of 3—5 years.

No information is available on diseases and pests affecting paper mulberry in South-East Asia. Bacterial blight caused by Pseudomonas syringae pv. broussonetiae is a disease of paper mulberry in Japan. It also affects Broussonetia kazinoki, but not mulberry (Morus spp.). In China the fungi Phytophthora boehmeriae and Dendryphiella broussonetiae attack paper mulberry. Paper mulberry is a host of Agrobacterium tumefaciens, which causes tumorous growth. A pest of paper mulberry in China is Apriona germari (Coleoptera, Cerambycidae).

In the Moluccas, paper mulberry stems are cut when they have a diameter of 2.5—5 cm, because older trees have a harder and more brittle bark. In Java, trees not older than 2 years are generally harvested for traditional papermaking. In Japan, stems from coppiced paper mulberry are usually harvested every 3—5 years.

In Thailand paper mulberry, spaced 1 m x 1 m apart and harvested 6 and 12 months after planting yielded 2400 and 2800 kg bark per ha, respectively. In Indonesian plantations at 800 m altitude, 2-year-old trees, 2—3 m tall, with a stem diameter of 2 cm, yielded about 300 g fresh bark per tree, equivalent to 90 g dry bark fibre.

For the traditional production of 'deluwang' paper from paper mulberry in Java and Madura, bark removed from stem pieces about 1.5 m long is cut in strips 5—6 cm wide, the outer bark is removed, and the strips are laid on a beam 20 cm wide and pounded until they are about double in width. The pounded strips are put in water, rinsed, and wrung out. Subsequently, they are folded lengthwise and then in four. They are pounded again until double sheets 50 cm wide have formed. These double sheets are first dried, then soaked, pressed out, folded, and rolled up in banana leaf. By heating for 5—6 days, the two sheets adhere. The resulting sheet is spread out, rubbed, stretched over a stem of the banana tree and dried in the sun. When dry, the side attached to the stem is smooth, the other side rough. The rough side is smoothened by rubbing with a smooth shell. The piece of paper finally obtained is about 50 cm x 37 cm. Cloth is made in a similar way. In the Moluccas the harvested stems are scorched carefully over a fire and the outer bark is pulled off, then the inner bark is peeled and dried. When needed for new clothes, the dried bark is soaked and prepared in a way similar to 'deluwang' paper in Java.
In the production of handmade paper in Japan, the stems are steamed to loosen the bark. The outer bark is scraped off to be used for inferior papers, whereas the inner bark is washed, kneaded in water, rinsed, and laid in the sun for drying and bleaching. Fibres are separated by boiling in a strong alkaline solution and beating with a mallet. The resulting pulp is mixed with water and gums. The pulp solution is scooped up with paper moulds, consisting of fine mesh sieves, with excess water draining away. When the fibre sheets are solid enough, they are removed from the mould and laid in a pile of alternating layers of wet paper and felt. The pile is pressed to remove water, and the sheets are removed from the felt and dried. In Burma (Myanmar), pulp is obtained by pounding the bast with water and boiling it with lime. The pulp is spread thinly over coarse cloth and allowed to dry to form paper.
The general procedure in the manufacture of tapa cloth is to peel bark strips off the stem and to remove the outer bark. After being soaked in water and cleaned, the strips are placed on a log and beaten. Individual strips are united by overlapping the edges and beating them together. Depending on the thickness, the appearance varies from muslin-like to leathery. Tapa cloth is often dyed or otherwise ornamented.

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

The exploitation of paper mulberry, especially as a source of raw material for speciality papers, e.g. for decoration and currency notes, could have some future and economic potential in South-East Asia. Production could be increased by using adapted cropping methods, the selection of appropriate cultivars and improved processing methods. Compounds from the bark may have some therapeutic potential in inflammatory diseases.

Backer, C.A. & Bakhuizen van den Brink Jr, R.C., 1965. Flora of Java. Vol. 2. P. Noordhoff, Groningen, the Netherlands. pp. 15—16.
Barker, C., 2002. Broussonetia papyrifera, Moraceae. Curtis's Botanical Magazine 19: 8—18.
Bhat, R.V. & Guha, S.R.D., 1952. Indigenous cellulosic raw materials for the production of pulp, paper and board. Part 4. Writing and printing papers from paper mulberry (Broussonetia papyrifera). Indian Forester 78: 93—97.
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Heyne, K., 1927. De nuttige planten van Nederlandsch-Indië [The useful plants of the Dutch East Indies]. 2nd Edition. 3 volumes. Departement van Landbouw, Nijverheid en Handel in Nederlandsch Indië. (3rd Edition, 1950. W. van Hoeve, 's Gravenhage, the Netherlands / Bandung, Indonesia). pp. 547—550.
Ilvessalo-Pfäffli, M.-S., 1995. Fiber atlas: identification of papermaking fibres. Springer-Verlag, Berlin, Germany. pp. 348—349.
Manas Kumpukul & Somsak Chaimongkal, 1990. Suksa kan pluk kan khayai phan lae kan kepkieo tonsa phua pen watthudip samrap tham yua kradat lae kradat sa [Studies on plantation, propagation and harvesting of paper mulberry for the raw material of paper pulp and Sa-handmade paper]. Kasetsart University, Bangkok, Thailand. 29 pp.
Suleman, K.M. & Nadeem, K., 1995. Suitability of home grown paper mulberry (Broussonetia papyrifera) for pulp and paper manufacture. Pakistan Journal of Forestry 45(4): 158—162.

C.C. Berg

Berg, C.C., 2003. Broussonetia papyrifera (L.) L'Hér. ex Vent.. In: Brink, M and Escobin, R.P. (Editors): Plant Resources of South-East Asia No 17: Fibre plants. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea