Imperata (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Imperata Cirillo

Protologue: Pl. rar. neap. 2: 26, t. 11 (1792).

Family: Gramineae

Chromosome number: x= 5; I. cylindrica: 2n= 20

• Imperata conferta (J.S. Presl) Ohwi,
• I. cylindrica (L.) Raeuschel.

• Cogon grass (En)
• Indonesia: alang-alang
• Philippines: kogon.

Imperata comprises about 8 species, occurring in tropical and subtropical regions. I. conferta and I. cylindrica are found throughout the Malesian region.

The uses (including medicinal) of I. cylindrica and I. conferta are very similar and both are in general used indiscriminately. I. cylindrica is reported to be used in various countries in South-East Asia for a wide range of medical problems such as fever, nausea, dropsy, jaundice, asthma, haematura, influenza, internal haemorrhages, nose bleeding, cough and kidney diseases. A decoction of the rhizome is commonly applied to purify the blood, as a diuretic and in the treatment of diarrhoea and dysentery.

Both Imperata species are an important source of roofing material, readily available and durable. When young, they may be used as fodder for ruminants. Both species have been used for making paper. The aggressive rhizomatous growth makes them suitable for erosion control and stabilizing slopes, despite their weedy characteristics.

Imperata is used only locally and has no importance in international markets.

The rhizomes of I. cylindrica contain the biphenyl ethers cylindol A and B, the phenolic compound imperanene, the sesquiterpenoid cylindrene, and the lignans graminone A and B. Cylindol A has shown 5-lipooxygenase activity, which may be partly involved in the reputed anti-inflammatory activity of I. cylindrica. Imperanene has shown inhibitory activity against rabbit platelet aggregation. Cylindrene and graminone B have shown inhibitory effects on rabbit aorta contraction. I. cylindrica has also been found to contain 5-hydroxytryptamine (serotonin) and the triterpenoids arundoin, cylindrin, fernenol, isoarborinol and aimiarenol. The rhizome has been found to contain 19% sugars (saccharose, dextrose, fructose, xylose) and various acids (including malic, citric, tartaric, chlorogenic, coumaric and oxalic acid). An aqueous extract of stem and leaves is reported to have shown some antitumour activity against sarcoma 180 and adenocarcinoma 75 in mice. Although I. cylindrica is widely considered to have diuretic properties, this could not be confirmed in a recent double blind study. Besides the above pharmacological activities, antiviral, antihepatotoxic, antihistamine and larvicidal activities are also reported.

• Rhizomatous, herbaceous, unbranched perennials up to 150(-300) cm tall, with deep, branched, fleshy rhizomes; culms with solid internodes.
• Leaves mostly basal, leaf sheath non-auriculate, with a fringed membranous ligule; leaves sometimes pseudopetiolate, without cross venation, persistent.
• Inflorescence a spiciform panicle, cylindrical; spikelets paired, homologous, bisexual, 3-6 mm long, 2-flowered, at the base with a dense whorl of silky white hairs, unequally pedicellate in each pair.
• Glumes 2, more or less equal; lower floret reduced to a hyaline lemma; upper floret fertile, stamens 1-2, ovary glabrous.
• Fruit an ellipsoidal caryopsis, about 1 mm long, brown.

I. cylindrica is a prolific seed producer and the light seeds are readily dispersed by wind. There is no dormancy and seeds may give 95% germination within one week after fruit maturation. The optimum temperature for growth is about 30°C with negligible growth at 20°C and 40°C. Some individual plants flower frequently, some never flower, and others are intermediate. The rhizomes are highly competitive and penetrate the roots of other plants, causing rot or death. In a controlled greenhouse experiment young plants initiated new rhizomes between the third and fourth leaf-stages. Rhizome growth is determinate, with the apical bud forming a shoot and sub-apical buds forming rhizome branches. Under favourable conditions apical and sub-apical buds develop simultaneously, but under stress the growth of the apical bud is favoured. Roots and buds develop at the distal nodes of the young rhizome long after the rhizome has been formed. Flowering is in general promoted by burning, and follows a few weeks after the fire.

Imperata is divided into two sections, based on the number of stamens: section Imperata (2 stamens) with only 1 species (I. cylindrica), and section Eriopogon Endl. (1 stamen). A number of varieties have been described for I. cylindrica, often pertaining to geographical regions. However, as these varieties more or less intergrade, the distinction is at present generally ignored.

I. cylindrica is often found in areas receiving more than 1000 mm rainfall/year, but has been recorded in sites receiving 500-5000 mm annual rainfall. It can withstand waterlogging but not continuous flooding. It grows at altitudes from sea-level up to 2000 m in several countries and has been recorded at 2700 m in Indonesia. Whereas I. cylindrica may have originally been restricted to infertile and acid soils in the tropics, it has become widespread through man's intervention, particularly following slashing and burning of forest lands. Its resistance to burning is associated with its vigorous underground rhizomes, but seedlings also establish after burning. It is found in a wide range of habitats, including the dry sand dunes of seashores and deserts, as well as swamps and river valleys. It grows in grassland, cultivated areas, and plantations. It quickly invades abandoned farmland and occurs on railway and highway embankments and in deforested areas. It is regarded as a light-loving plant and will not persist under heavy shade in plantations. Although it grows in a wide range of soil types of widely differing fertility, it grows most vigorously in wet soil of reasonable fertility. It has been reported to grow on soils with pH 4.0-7.5. It can even tolerate very hot, steamy and sulphurous conditions near an active volcanic fumarole or vent. I. cylindrica is reported to have allelopathic properties that adversely affect the growth of other plants.

Imperata is seldom propagated deliberately, but spreads by rhizomes and seed. Rhizomes accidentally cut by cultivation can reestablish from pieces with as few as 2 nodes.

Imperata is favoured by burning, which can lead to virtually monospecific swards. If it is to be used for thatching, swards are left ungrazed until after the mature growth has been removed. It can be eliminated by heavy continuous grazing; vigour will be reduced by close, frequent cutting and rhizomes can be destroyed by frequent intensive cultivation. It has been suggested that I. cylindrica that is used regularly for grazing should be grazed rotationally when 15-25 cm high. Because of its aggressiveness and low quality as forage, I. cylindrica is widely regarded as a weed. It is considered to be one of the most pernicious weeds in South-East Asia. In Indonesia, it is considered to be one of the three most important weeds (the others being Echinochloa crus-galli (L.) P. Beauv. and Monochoria vaginalis (N.L. Burmann) Kunth), and to be the single most important weed in perennial crops.

Imperata is either grazed when young or cut for thatch when mature. To collect the medicinally important rhizomes, plants are simply uprooted.

Reported above-ground dry matter yields of I. cylindrica are 2-11 t/ha per year. In Indonesia per ha production was found to be 11 t of leaves and 7 t of rhizomes, with on average 4.5 million shoots.

Imperata is widespread and common throughout Malesia, in general favoured by human activities, and therefore certainly not endangered. There are no known breeding programmes on Imperata.

Although Imperata is widely considered a serious weed, it can be useful for various purposes, especially to provide fodder when young and thatching material when mature. A broad range of medicinal uses has been reported, but most claims still need to be validated, though compounds that have shown vasodilative activity, anti-inflammatory properties or inhibition of platelet aggregation have been isolated.

• Aguilar, N.O., 1992. Imperata cylindrica (L.) Raeuschel. In: 't Mannetje, L. & Jones, R.M. (Editors): Plant Resources of South-East Asia No 4. Forages. Pudoc Scientific Publishers, Wageningen, the Netherlands. pp. 140-142.
• Falvey, J.L., 1981. Imperata cylindrica and animal production in South-East Asia: a review. Tropical Grasslands 15: 52-56.
• Holm, L.G., Plucknett, D.L., Pancho, J.V. & Herberger, J.P., 1977. The world's worst weeds. Distribution and biology. East-West Center. The University Press of Hawaii, Honolulu, United States. pp. 62-71.
• MacDicken, K.G., Hairiah, K., Otsamo, A., Duguma, B. & Majid, N.M., 1997. Shade-based control of Imperata cylindrica: tree fallows and cover crops. Agroforestry Systems 36: 131-149.
• Matsunaga, K., Ikeda, M., Shibuya, M. & Ohizumi, Y., 1994. Cylindol, a novel biphenyl ether with 5-lipoxygenase inhibitory activity, and a related compound from Imperata cylindrica. Journal of Natural Products 57(9): 1290-1293.
• Matsunaga, K., Shibuya, M. & Ohizumi, Y., 1994. Cylindrene, a novel sesquiterpenoid from Imperata cylindrica with inhibitory activity on contractions of vascular smooth muscle. Journal of Natural Products 57(8): 1183-1184.
• Matsunaga, K., Shibuya, M. & Ohizumi, Y., 1994. Graminone B, a novel lignan with vasodilative activity from Imperata cylindrica. Journal of Natural Products 57(12): 1734-1736.
• Matsunaga, K., Shibuya, M. & Ohizumi, Y., 1995. Imperanene, a novel phenolic compound with platelet aggregation inhibitory activity from Imperata cylindrica. Journal of Natural Products 58(1): 138-139.
• Terry, P.J., Adjers, G., Akobundu, I.O., Anoka, A.U., Drilling, M.E., Tjitrosemito, S. & Utomo, M., 1997. Herbicides and mechanical control of Imperata cylindrica as a first step in grassland rehabilitation. Agroforestry Systems 36: 151-179.
• Watson, L. & Dallwitz, M.J., 1992. The grass genera of the world. C.A.B. International, Wallingford, United Kingdom. pp. 470-471.

• Imperata conferta
• Imperata cylindrica

• Juliana Jonathan & Bambang P.J. Hariadi