3244

9: Plants yielding non-seed carbohydrates

Tacca leontopetaloides (L.) O. Kuntze

Rev. gen. pl. 2: 704 (1891).

TACCACEAE

2n = 30

Tacca pinnatifida J.R. & G. Forster (1775), Tacca involucrata (Limpr.) Schum. & Thonn. (1827), Tacca viridis Hemsley (1899).

East Indian arrowroot, Polynesian arrowroot, Tahiti arrowroot (En). Indonesia: gadung tikus (Indonesian), kecondang (Javanese), taka laut (Sumatra). Malaysia: lukeh, poko lukeh. Papua New Guinea: masoa, pia. Philippines: gaw-gaw (Tagalog), tayobong (Bisaya), panarien (Ilokano). Thailand: thaoyaimom (central), buk-ro (eastern). Vietnam: b[aj]ch tinh, c[ur] n[uw]a.

The exact origin of Tacca leontopetaloides is not known but is thought to be in Malesia where the other species of the genus have their greatest variability. It is widely distributed wild and sometimes cultivated throughout the tropics of Africa, Asia, Australia and Oceania, from West Africa to India, throughout South-East Asia and in the Pacific as far as Easter Island.

Although fresh tubers are inedible because of the presence of bitter toxic substances, they can be eaten after thorough preparation or, more important, an edible starch can be extracted from them. The starch can be used for baking bread, making pastes and puddings, often mixed with other ingredients like, for example, sugar, coconut juice, fruit pulp, wheat flour and flavourings. The cooked starch is easily digestible and is suitable for patients with digestive problems. In Fiji, undried starch is wrapped in leaves and buried into the ground to ferment before being eaten. In Samoa, fresh starch is used as a kind of glue between thin layers of beaten bark of the paper mulberry (Broussonetia papyrifera (L.) Ventenat) to make bark cloth ('tapa' or 'siapo'). The starch is also used for starching clothes and to make sweetmeats. In Gabon, the fruit pulp is eaten by children. Sometimes the leaves are used as a vegetable. The petioles and peduncles yield fibres that are used for making hats and fishing utensils. In traditional medicine the tubers and their starch are used against dysentery, diarrhoea and oedemas.

At present East Indian arrowroot is widely but only locally produced or collected and traded, and no statistics are available. In the past its role as a staple food was more important, especially in the Pacific Islands, where, for example, Hawaii, Tahiti and Fiji, exported about 5 t rough East Indian arrowroot material per year. Once it was also important in Thailand. Its role as staple food has largely been taken over by cassava. In many places, East Indian arrowroot is now considered as an emergency food.

The composition of fresh tubers per 100 g is approximately: skin 2—3 g, fibre 6—7 g, starch 20—30 g and waste material 60—70 g. The starch extracted from the tubers is very white, much resembling cassava starch; the grains are simple polyhedrons or hemispheres, (8—)20(—40) µm in diameter. The analysis on a dry weight basis, for a tuber originating from Ivory Coast was: protein 5.1%, fat 0.2%, carbohydrates 89.4%, cellulose 2.1%, ash 3.2%, Ca 0.27% and P 0.2%. A bitter extract (about 2.2%) was also isolated from the tuber, containing ß-sitosterol, cerylic alcohol, taccalin (a rather unusual, bitter principle in plants), alkaloids and steroidal sapogenins. Small young tubers are said to be more bitter than large older ones. The sapogenins have shown a strong activity against snails (Bulinus truncatus and Biomphalaria pfeifferi).

A perennial, erect, stemless herb, up to 3 m tall, with tuberous rhizome. Tuber depressed globose or broadly ellipsoidal, up to 20 cm in diameter, weighing up to 0.9 kg, usually smaller and lighter, thin-skinned, smooth, white when young, turning dark grey to brown, white and somewhat juicy within, growing near the surface up to 50 cm deep, renewed annually, provided with an apical cavity from which the leaves and inflorescences emerge. In young plants the base of the leaves and the inflorescence is surrounded by a special, linear-lanceolate leaf (cataphyll), 8—21 cm 1—3 cm. Leaves 1—3; sheath 2—25 cm 3.5 cm; petiole hollow, cylindrical, 17—150 cm long, 0.3—2.5 cm in diameter, light green, with white-green to blackish-purple dots, ridged longitudinally; blade broadly obovate, ovate or oblong-ovate in outline, up to 70 cm 120 cm, glabrous, palmately 3-sect, with the 3 segments lobed to dissected into orbicular to linear lobes. Inflorescence 1—2 per plant, umbel-like, 20—40-flowered; peduncle (scape) hollow, 20—170 cm long, 0.2—2.5 cm in diameter, green, ridged longitudinally; involucral bracts of different size, 4—12, in 2 whorls, ovate to ovate-lanceolate, up to 10 cm 3.5 cm, green; floral bracts filiform, 20—40, up to 25 cm long, purple or dark black-brown; flowers bisexual, regular, campanulate, drooping, 6—17 mm 6—13 mm, yellowish to black-purplish-green; pedicel up to 6 cm long, in fruit up to 8 cm long; perianth fleshy, persistent, tubular and ending in 3 outer and 3 inner lobes; stamens 6, white, yellow, brown or purple, adnate to perianth segments, with short and flattened filaments which at top are free and helmet-shaped and hood the anthers; pistil on annular, ribbed, glandular-hairy disk, ovary unilocular, style short, stigma 3-lobed and umbrella-shaped with stigmatic surface beneath. Fruit subglobose, ovoid or ellipsoid, berry-like, up to 3.5 cm 1.5—2.5 cm, pendulous, pale orange, many-seeded. Seed flattened ovoid to ellipsoid, 5—8 mm 3—5 mm 1.5—3 mm, 15—19-ribbed, glabrous, yellow-brown, but surrounded by a spongy white aril.

Tacca leontopetaloides exhibits a seasonal growth rhythm. During the growing season, the tuber is replaced by a new main tuber which arises from a downward-growing runner-like thick rhizome at a lower level, and remains dormant after the yearly death of the aerial parts of the original plant until the new growing season. Secondary smaller runners, also forming tubers, may emerge above the old tuber and spread downwards. This cycle takes about 8—10 months, with 2—4 months of dormancy. In Malesia, flowering and fruiting may occur in all months of the year, but the aerial parts usually die off between December and March. It is not known whether a plant flowers more than once on the same tuber, but relatively older plants have relatively larger vegetative and generative parts. Plants grown from seed first produce palmately incised young leaves, and the mature leaves are 3-lobed with each lobe pinnately lobed; such plants do not start flowering until 2—3 years old. Most probably, pollination is effected by insects.

Due to its wide geographic distribution, many local forms have been described as species, subspecies, varieties or formas. Those forms were largely based on leaf characteristics, which are very variable indeed, depending on the environment and the age of the plant, but none deserves separate taxonomic distinction. Sometimes Tacca leontopetaloides in the vegetative stage is confused with Amorphophallus species, but it can be distinguished immediately by its ribbed hollow petioles, which in Amorphophallus are solid, smooth and usually flecked. It is possible (but no records are available) that some other tuber or tuberous rhizome-producing Tacca species are occasionally used in South-East Asia as emergency food, e.g. Tacca ebeltajae Drenth (Papua New Guinea, Solomon Islands; tuber globose to subcylindrical, up to 6 cm long and 2 cm in diameter), Tacca integrifolia Ker-Gawler (Sumatra, West Java, Borneo and continental South-East Asia; rhizome cylindrical, up to 12 cm 3 cm), and Tacca palmata Blume (throughout South-East Asia; tuber globose to ellipsoidal, up to 8 cm long and 3 cm in diameter).

The natural habitat of Tacca leontopetaloides is distinctly the beach. In its distribution area, however, it is very indifferent to climate, soil, and vegetation. It rarely occurs in heavy shade and in primary forest, frequently in coastal vegetation, usually below 200 m, occasionally up to 1100 m altitude. It often grows in small groups, on and behind the seashore, in grasslands, alang-alang fields, thickets, savannas, moist or dry primary or secondary forests, coconut plantations and is often associated with beach vegetation of e.g. Casuarina, Pandanus, Scaevola, Barringtonia and Eucalyptus species.
Seeds can be dispersed by sea water, the spongy testa enabling them to float for many months, but nothing is known about the influence of sea water on their viability. Its occurrence on many Pacific islands suggests the possibility of dispersal by sea. Fruits are eaten by a white-eyed bird (Zosterops masii), which might also disperse the seed. Without doubt, the most important distributor of East Indian arrowroot has been man, mainly by planting tubers.

Tacca leontopetaloides can be propagated by seed and by tuber. Usually, small secondary tubers are planted 15 cm deep, in rows at a spacing of 60—90 cm 45 cm, preferably at the beginning of the rainy season. It is reported that the crop benefits greatly from weeding and partial shade, and no serious diseases or pests are known. When the leaves begin to wither the tubers can be harvested by digging them up. Individual tubers normally weigh 70—340 g, but may reach 900 g. They may be stored in pits for later use but are liable to sprouting. Harvested tubers are peeled, grated, washed several times in hot or cold water, and after the starch has settled, the water is removed and the starch dried.

Neither germplasm collections nor breeding programmes are known to exist for Tacca leontopetaloides. Germplasm collection is urgently recommended, as in many places its natural habitat is being rapidly destroyed.

The economic importance of Tacca leontopetaloides will remain quite invisible in official statistics. It undoubtedly remains important at the local level as a reserve food. Its ability to produce edible starch on marginal soils is of interest. More research is needed to investigate the feasibility and economics of large-scale production.

Abdel-Aziz, A.M.E., 1989. Molluscicidal activity of the Sudanese plant, Tacca leontopetaloides. PhD dissertation. Institute of Science and Technology, University of Wales, United Kingdom. 265 pp.
Barrau, J., 1962. Les plantes alimentaires de l'Océanie, origines, distribution et usages [The edible plants of Oceania, origins, distribution and uses]. University of Aix-Marseille, Faculty of Sciences, Thesis No 71. pp. 107-109.
Drenth, E., 1972. A revision of the family Taccaceae. Blumea 20(2): 367-406.
Kay, D.E., 1973. Crop and product digest No 2. Root crops. The Tropical Products Institute, London, United Kingdom. pp. 57-60.
Phengklai, C., 1980. Taccaceae. Thai Forest Bulletin 13: 23-33.
Purseglove, J.W., 1972. Tropical crops. Monocotyledons 2. Longman, London, United Kingdom. pp. 517-518.
Scheuer, P.J., Swanholm, C.E., Madamba, L.A. & Hudgins, W.R., 1963. The constituents of Tacca leontopetaloides. Lloydia 26(3): 133-140.

J. Jukema & Y. Paisooksantivatana

Jukema, J. & Paisooksantivatana, Y., 1996. Tacca leontopetaloides (L.) O. Kuntze. In: Flach, M. & Rumawas, F. (Editors): Plant Resources of South-East Asia No 9: Plants yielding non-seed carbohydrates. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea