Prota 2: Vegetables/Légumes
Caesalpiniaceae (Leguminosae - Caesalpinioideae)
Tara nut (En). Tara (Fr).
Origin and geographic distribution
Lemuropisum edule is restricted to the most southern part of Madagascar with two disjunct populations some 60 km apart. One population is known near Itampolo and the second around Lake Tsimanampetsotsa.
The immature fruits of Lemuropisum edule provide a local food. Seeds are eaten raw, after discarding the brittle testa. They are apparently not used in cooking. Goats browse the shrubs when there is little else to eat; they also eat the seeds.
The flavour of green seeds of Lemuropisum edule is reminiscent of fresh garden peas. The cotyledons are agreeably sweet with a cashew-like flavour, smooth consistency and a flexible, rather plastic texture. The seeds contain 38–43% available carbohydrates, 26–32% unavailable carbohydrates, 14–26% protein and 6–9% fat. However, the ingestion of 100 g kernels (c. 85 raw seeds) may inhibit human production of chymotrypsin and cause digestive upsets; this may be reduced by cooking or roasting. Per 100 g dry matter, seeds contain 1–5 g trans-3-hydroxy-L-proline, mature leaves 1–2 g. Hydroxyproline showed potent antifeedant activity against larvae of Spodoptera spp. It is cytotoxic to human fibroblast cells. A second potentially toxic amino acid, azetidine-2-carboxylic acid, has been identified in the seed. Consumption of small quantities is unlikely to cause poisoning, but the long-term physiological effects still need to be assessed.
Shrub up to 6 m tall, many-stemmed and much branched, lateral shoots terminating in rigid spines. Leaves alternate, in tight clusters, paripinnate with 1–4 pairs of leaflets; stipules small, caducous; leaflets ovate to orbicular, 3.5–6 mm long. Inflorescence an axillary raceme. Flowers bisexual, almost regular, 5-merous; calyx with leathery lobes; petals free, clawed, the upper ones slightly larger, white, tinged yellow; stamens 10, free; ovary superior, sessile, 1 -celled, style slender, stigma punctate. Fruit a pendent, compressed-cylindrical pod 20–30 cm × 2 cm, constricted between the seeds, densely grey pubescent, spirally dehiscent with 2 valves, 6–16-seeded. Seeds ovoid-reniform, c. 2.5 cm × 1.5 cm, seedcoat cream-white, thin and brittle.
Lemuropisum comprises a single species and is closely related to Colvillea and Delonix. Two growth forms have been distinguished: a spreading shrub and a less common, compact shrub with erect branches.
Lemuropisum edule appears to be confined to an exposed seaward-facing rocky limestone escarpment and sandy soils immediately below them, at 15–100 m altitude. The rainfall in the area is bimodal and very erratic, with an annual average of less than 400 mm. The average temperatures are 27°C in summer and 20°C in winter. In cultivation the plant prefers alkaline soils.
Lemuropisum edule is not cultivated in Madagascar nor sold on local markets. The species has been under investigation as a potential crop in western Australia. Seeds need to be stored at low temperatures and low relative humidity. They can be sown in 20 cm long bags. Germination is rapid after soaking for 10 hours. Aerial growth is characteristically zigzag with rapid development of side branches, requiring plants to be well spaced in the nursery to prevent entanglement. Transplanting can be done after 3 months at a spacing of 4 m × 4 m.
Genetic resources and breeding
The distribution of Lemuropisum edule is restricted and fragmented. The species is threatened by intensive grazing, especially in the main population site around Itampolo. It is therefore classified as endangered by IUCN.
Lemuropisum edule has potential as a vegetable for arid areas if toxicity barriers are overcome. It has further potential for windbreaks and hedges. A survey of the extent and the genetic variation of the natural populations and measures for its conservation are required. Other obvious steps are to establish provenance trials, to select high-yielding, toxin -free trees and to evaluate the two growth forms. The potential for micropropagation and production in arid regions in the tropics needs to be investigated, as well as its agronomic requirements.
Prolines are promising for treating excessive collagen production in humans and as inhibitors of tumours that require collagen for growth. Lemuropisum edule could provide a useful source of proline for research purposes.
• du Puy, D.J., Labat, J.N., Rabevohitra, R., Villiers, J.-F., Bosser, J. & Moat, J., 2002. The Leguminosae of Madagascar. Royal Botanic Gardens, Kew, United Kingdom. 750 pp.
• du Puy, D.J., Phillipson, P.B. & Rabevohitra, R., 1995. The genus Delonix (Leguminosae: Caesalpinioideae: Caesalpinieae) in Madagascar. Kew Bulletin 50(3): 445–475.
• FAO, 1995. Edible nuts. 2nd edition. Non-wood forest products No 5. FAO, Rome, Italy. 209 pp.
• Kite, G.C., Plant, A.C., Burke, A., Simmonds, M.J.S., Blaney, W.M. & Fellows, L.E., 1995. Accumulation of trans-3-hydroxy-L-proline by seeds and leaves of the edible Madagascan legume Lemuropisum edule H. Perrier. Kew Bulletin 50(3): 585–590.
• Banks, H., 1997. The pollen of Delonix (Leguminosae: Caesalpinioideae: Caesalpinieae). Kew Bulletin 52(2): 417–434.
• Schatz, G.E., 2001. Generic tree flora of Madagascar. Royal Botanic Gardens, Kew, United Kingdom. 477 pp.
Correct citation of this article:
Bosch, C.H., 2004. Lemuropisum edule H.Perrier In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.