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Ethnobotanical Leaflets 14: 864-74. 2010. Horse Eye
Bean, Mucuna sloanei Fauw. &
Rendle (Fabaceae)]: An Underutilized Agro Biodiversity Resource in South Gordian Chibuzo Obute Department of Plant Science and Biotechnology E-mail goddie_chi@yahoo.com Issued: August 1 2010 Abstract In south eastern Key words: Agro biodiversity,
morphology, ethnobotany, malnutrition, legume. Introduction The neglect this scenario has brought on the utilization of some botanically useful products has been phenomenal. Some of the forest products are not staples but rather spices and condiments which are used as food adjuncts. The ingenious thing about these is that some food condiments are so nutritious that they also complement the food eaten by the people. One such plant is Mucuna sloanei Fauw. & Rendle (Synonym : Mucuna urens
auct. non (L.) Medik.) in the Family Fabaceae. It is a source of
dietary protein as it is a legume. However, it is sliding into the endangered
species list because its utility and cultivation has been neglected over the
years especially in the south eastern parts of M. sloanei is usually cultivated around homes and gardens mostly for immediate family culinary or other subsistence purposes. Although the plant has been described by earlier workers, much still needs to be described in the species. This is pertinent in that one of the world’s problems is not only availability of food, but adequate nutrition for people in the third world. The aim of the current effort is to document the morphological description of this plant, its great nutritional potentials for nourishment of humans and other ethnobotanical uses. It would also highlight its neglected and underutilized status and suggest ways of increasing its utility because of its unpopularity with most Nigerians. Taxonomic Classification: Kingdom:
Plantae – Plants Subkingdom:
Tracheobionta – Vascular
plants Superdivision:
Spermatophyta – Seed plants Division: Magnoliophyta – Flowering plants Class: Magnoliopsida –
Dicotyledons Subclass: Rosidae Order: Fabales Family: Fabaceae – Pea family Genus: Mucuna Adans. – Mucuna Species: Mucuna sloanei Fawc. & Rendle – horseeye bean Distribution The distribution of this species is as follows:
It is the same plant known with the synonym Mucuna urens. Hutchinson and Dalziel (1958) noted that lateral leaflets are differently shaped from the terminal ones. Generally the leaflets are obliquely ovate, the flowers are cream or yellow, fruits are obliquely transversely ridged with urticating bristles, green initially but turn black when mature. Materials and methods Some local government areas, towns and villages around Results and Discussion. Macro morphological description. The plant is a perennial liana producing several fruits annually. It twines around upright supports in an anti-clockwise manner. Stem is covered with leaf scares and has characteristic silver coloured patches (Fig. 1 A).
Psidium guajava tree, B. The leafy shoot of same plant ramifying the P. guajava.
Fig. 2. A trifoliate sprigg of M. sloanei bearing papilionaceous flowers and a single pod (fruit).
A.
B. Fig. 3. Inflorescences of M. sloanei usually bear 2-10 flowers. A. Closed flowers Suggesting cleistogamy. B. Anthesis in a flower (yellow arrow) and a fly (white arrow) evidence of entomophily. Leaves alternate, pinnately 3-foliolate; stipules caducous; petiole 5–11 cm long, rachis 2–3 cm long; petiolules 3–4 mm long; leaflets ovate to elliptical, 7–11 cm × 4–7 cm, apex acuminate, lateral leaflets asymmetrical, silky pubescent below (Fig 1B and Fig 2). Inflorescence an axillary, umbellate raceme, 5–10-flowered. Flowers bisexual, papilionaceous; pedicel c. 1 cm long; corolla up to 7 cm long, yellow-green to whitish yellow; stamens 10, 1 free and 9 united; ovary superior, 1-celled, style long (Fig 3A). Fruit a flattened-cylindrical pod 10–14 cm × 4–5 cm × 1 cm, blackish, with 12–15 transversal deep furrows, bearing yellowish stinging hairs, 2–3-seeded. Seeds are discoid, c. 3 cm in diameter. Individual flowers are cleistogamous presupposing pollination prior to flower opening. However, evidence of exposure of anthers and stigma during anthesis for possible entomophyly is seen in Fig. 3B with yellow arrow indicating this condition while the white arrow actually shows an insect hunting for nectar.
Fig. 4. Unripe pods (fruits) of M. sloanei. These fruits will soon be ready for harvesting. The fruits or pod of the plant are characteristically ridged with sometimes completely spiral, hairy ridges and sometimes ridges are incomplete (Fig. 4). They are green when unripe but turn black at maturity. The fruit skin is tough and fibrous and water resistant. It occurs as a bunch after the inflorescence arrangement. Each fruit may contain from 1 to 4 or 5 seeds. The seeds are cream coloured and almost entirely ringed with white aril (Fig. 5A) when young but turn jet black at maturity with the aril persisting (Fig. 5B). The seed is tough, velvety and highly water-resistant and thus has long dormancy period. Its appearance when the aril and the rest of the seed are considered is like a hamburger hence the common name of “Hamburger seed” (Fig 6).
A.
B. Fig. 5. Exposed seed of Mucuna sloanei. A. Seed in an unripe fruit. B. Seed in a ripe Fruit. Notice the velvety cream and the white crescent-shaped aril around the hilum which persists in the ripe pod. Prioritization of the crop. Farmers interviewed do not see the horse eye bean as priority plant. It is rather an adjunct crop in yam and cassava farms which are crops of main interest. Another point emphasized by the farmers is that patronage is not as sure as with other
processing into soup condiment or used for planting. plants. The reason is that the processing is elaborate and cumbersome.
For instance, before the endosperm is used as food there is a long period of
boiling to soften the tough seed coat. Deshelling is another labour intensive
process because is done manually. Moreover, the endosperm would be pounded
into a powder with mortar and pestle before using it as food condiment.
Generally, interest in its cultivation is waning for these reasons. Potentials of the crop. M. sloanei has both
nutritional and chemoprotective properties that were of benefits to humans
and livestock (Ijeh, et al., 2008). With proximate crude
protein content of 28.18±0.25%, 4.31±0.09% fat, crude fibre of 9.60±0.05%,
ash 4.19±0.01% and carbohydrate content of 53.75±0.28% the seeds of M. sloanei compete comparatively with
other legumes and pulses as highly nutritious crops. Other factors of
importance in the crop include: presence of alkaloids, phytic acid, tannins,
flavonoids, haemoglutinin and oligosaccharides. Some of these factors occur
in most ethnomedicinally useful plant groups (Obute and Adubor, 2007). M. sloanei crop production needs
popularization for greater utility in meeting dietary needs of humans in
developing countries. Apart from its dietary uses in cooking soups in
southern Challenges facing M. sloanei Although Jansen (2007) reported that there is no immediate threat of genetic erosion yet cultivation is occasional, the crop’s survival is under serious threat from a combination of neglect, low priority arising from encumbrances of processing before utilization and degradation of the Nigerian tropical forest zone where it thrives. It is therefore the aim of this attempt to document its morphological features, potential food and ethnobotanical utility in the face of these challenges in order to sensitize research in better production approaches, processing strategies as well as potential utility in the fight against malnutrition in developing countries. Acknowledgements. I wish to thank the farmers who agreed to be interviewed for their contribution to agrobiodiversity conservation. References Obute, G.C. and Adubor, G. O. 2007. Chemicals
Detected in Plants Used For Folk Medicine in South Ijeh, Jansen, P.C.M., 2005. Mucuna sloanei
Fawc. & Rendle. [Internet] Record from Protabase. Jansen, P.C.M. &
Cardon, D. (Editors). PROTA (Plant Resources of Tropical Africa / Resources
végétales de l’Afrique tropicale), |
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