Borassus akeassii Bayton, Ouédr. & Guinko

Bayton, R. (2007). A Revision of Borassus L. (Arecaceae). Kew Bulletin, 62(4), 561-585. Retrieved from http://www.jstor.org/stable/20443389

Vernacular

Burkill (1997) lists a huge number of indigenous names for Borassus (ostensibly B. aethiopum) in West Africa and many of these may be applicable to B. akeassii. The French name r6nier (derived from the Wolof word r6n) is widely used in Francophone Africa for both Borassus species.

Note

Initial examination of B. akeassii suggests a close relationship with B. flabellifer, as suggested by previous authors (Ake Assi & Guinko 1996; Ouedraogo et al. 2002). The similarities are largely a matter of scale, as B. akeassii is considerably smaller than other African Borassus species. This has been attributed to the intensive extraction of sap leading to reduced growth (Porteres 1964). The small leaves, petiole spines, inflorescences and fruits are reminiscent of those of B. flabellifer. However, B. akeassii has a ventricose stem and that character is restricted to African Borassus. The pollen is particularly distinctive; the gemmae are denser and almost completely obscure the tectum whereas it is clearly visible in the pollen of all other Borassus species. Modern material collected from the type locality of B. aethiopum can be identified as that species. Borassus akeassii honours Professor Laurent Ake Assi (Abidjan University, Côte d'lvoire) who, together with Professor Sita Guinko (University of Ouagadougou, Burkina Faso) first distinguished the palm from B. aethiopum (Ake Assi & Guinko 1996).

Type

Burkina Faso, Comoe Province, 1 km S of Banfora, 20 Jan. 2004 (9), Bayton et al. 69 (holotype K!, isotypes FTG!, OUA!).

Morphology Stem

Stem to 15 m tall, almost always ventricose, to 80 cm diam., when stem marked by numerous irregular scars, this is caused by tapping

Morphology Leaves

Leaves glaucous, 8 - 22 in the crown; petiole and sheath 90 - 160 cm long; petiole 3.0 - 7.4 cm wide at midpoint, green, margins with small serrate black teeth (0.2 - 0.6 cm long), or teeth largely absent; costa 22 - 28 cm long; adaxial hastula conspicuous, to 2.4 cm, abaxial hastula rudimentary; lamina rather flat, radius to 160 cm maximum, dense indumentum on the ribs of some immature leaves; leaflets 45 - 82, 2.8 - 7.3 cm wide, apices acute and entire or splitting longitudinally with age, shortest leaflet 58 - 147 cm long, leaf divided to 60 - 99 cm; commissural veins 5 - 7 per cm, leaf anatomy isolateral.

Morphology Reproductive morphology Inflorescences

Pistillate inflorescences spicate or branched to one order; rachis ± 80 cm long, flower-bearing portion 24 - 39 cm long with ± 23 flowers arranged spirally Staminate inflorescences branched to two orders, upper subtending branches terminating in 1 - 3 rachillae; rachillae green-brown and catkin-like, 23 - 36 cm long, 2.3 - 2.5 cm diameter, usually with a mamilliform apex; rachilla bracts forming pits that contain a cincinnus of 5 - 10 staminate flowers.

Morphology Reproductive morphology Flowers Pollen

Pollen monosulcate, elliptical, 51 - 72 μm long, aperture 47 - 61 μm long, polar axis 49 - 61 μm long; tectum reticulate, densely covered with supratectal gemmae

Morphology Reproductive morphology Flowers

Pistillate flowers 3.5 x 3 cm, bracteoles 2 cm diam., sepals 2 x 2 cm, petals 1.5 x 1.5 cm Staminate flowers 0.4 - 0.6 cm long, exserted from the pits individually or in groups of 3 - 5; bracteoles 0.8 x 0.5 cm; calyx 0.5 x 0.2 cm, shallowly divided into three sepals, petal lobes 0.2 x 0.1 cm; stamens 6 with very short filaments, 0.1 x 0.03 cm, anthers, 0.1 x 0.05 cm; pistillode minute

Morphology Reproductive morphology Fruits

Fruits large, ± 15 cm long and ± 12 cm diameter, ovoid with a somewhat pointed apex, fragrant and yellowish green at maturity, produced inside persistent perianth segments; pyrenes 1 - 3, 6.8 - 9.3 cm x 5.4 - 7.5 cm.

Distribution

Restricted to West and Central Africa. Ake Assi and Guinko (1996) report that the palm is present in Benin, Burkina Faso, Côte d'Ivoire, Mali, Niger and Nigeria. Borassus akeassii (as Borassus sp. aff. flabellifer) has also been recorded in Senegal and the Central African Republic (Arbonnier 2002). However, the range of B. akeassii may be much wider than suggested due to misidentification of the palm as B. aethiopum. Johnson (1984) noted that Borassus aethiopum in Guinea-Bissau was used for wine production. He also noted that the palms have green, orange-sized fruits and both these facts suggest B. akeassii. This study can confirm the presence of B. akeassii in Burkina Faso and Senegal only. In addition, a specimen collected in southeastern Congo-Kinshasa (Liben 2822) has been identified as B. akeassii.

Ecology

Sudan savannas with 800 - 1100 mm annual rainfall. In Burkina Faso, most populations are semi managed for wine production. Seed is collected and planted and the palms often have crops planted beneath (usually cotton or cassava).

Conservation

Data deficient. Borassus akeassii may have a much wider distribution than is currently known. However, in the areas where it is known to occur, it is abundant and a significant crop for local people. Sambou et al. (2002; 1992) report that over exploitation is threatening populations of B. aethiopum in Guinea and Senegal, but it is possible that these refer to B. akeassii. In many cases, it is difficult to determine whether populations of B. akeassii are cultivated (i.e. planted) or merely wild plants that are exploited.

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation

Predicted extinction risk: not threatened. Confidence: confident