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    Variability of the critical frequency of the f2 layer, fof2 in west africa using ionosonde stations at ouagadougou and dakar
    (2012) Salami, O.R.; Nymphas, E.F.
    The critical frequency of the F2 layer of the ionosphere, foF2 is responsible for various effects on radio communication such as refraction, scintillation, absorption, error in Global Positioning System (GPS), jitter and phase delay. The variations of the critical frequency of the F2 layer at two different locations over West Africa were studied using ionosonde data for a solar cycle (1979 to 1989) at low, moderate and high solar activity, 1986, 1983 and 1989, respectively. The ionosonde stations are Dakar in Senegal (15°N, 17°W) and Ouagadougou in Burkina Faso (12°N, 1,8°W). The investigation of critical frequency of the F2 layer, foF2 using Relative Standard Deviation (RSD) revealed the spread and the occurrence of foF2. The results obtained in this study are proposed as equatorial input values for the development of a Variability Model for the International Reference Ionosphere.
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    Scanning electron microscopy of fruits in the West African polygonaceae
    (Institute of Botany, Chinese Academy of Sciences, 2010) Ayodele, A. E.; Zhou Z.
    The fruit morphology of 18 taxa representing seven genera of the family Polygonaceae in West Africa was investigated using scanning electron microscopy. The achenes are trigonous, lenticular, globose, subglobose, heart shaped, ovoid, or cone like. Sizes range from 0.12 × 0.10 cm2 in Polygonum plebeium to 7.87 × 0.58 cm2 in Afrobrunnichia erecta. Colors are brown to black. The cells are isodiametric in P. plebeium, irregular in A. erecta, Antigonon leptopus, and Harpagocarpus snowdenii, and polygonal in other species. The walls are straight, curved, or undulate and are either raised or depressed. Afrobrunnichia erecta is characterized by deeply sinuate lateral walls. The cell surface may be smooth or tuberculate or fibrillate in the family, usually covered with wax deposits. The combination of these characters is mainly taxonomically useful at the tribal level and rarely at the specific or infraspecific level for the delimitation of the taxa.
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    Scanning electron microscopy of leaves in the West African polygonaceae
    (2008-12) Ayodele, A. E.; Zhou Z. K.
    The leaf surfaces of the West African taxa of the Polygonaceae were studied using the Scanning Electron Microscope (SEM). Leaf epidermal cells arc polygonal, isodiametric and rarely irregular. Anticlinal walls are straight, curved, undulate or sinuate. Striae are present in a few taxa such as Polygonum plebeium. Rumex abysinaicus, R. bequaertii, Oxygonum sinuatum, Persicaria nepalensis and Afrobrunnichia erecta. The striae may be parallel, radiate, or randomly distributed. Trichomas are unicellular, uniseriate, aggregating together in some species of persicaria, while they may be flagelliform, interwoven and woolly in Persicaria senegalensis forma albotomentosa hence diagnostic for the species. Peltate glands are characteristic of A. arena. Stomata are mainly paracytic or anomocytic although diacytic. cyclocytic and anisocytic types may also be found in some taxa sometimes together with the main types. Stoma’s are sunken in a few species such as Polygonum plebeium and Persicaria attenuata subsp. pulchra, raised or at the same level with epidermal cells in other taxa. Wax deposits arc associated with the stomata in Persicaria attenuata subsp. africana. These characters are discussed in relation to the taxonomy of the family in West Africa.
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    The family polygonaceae in West Africa: taxonomic significance of leaf epidermal characters
    (Elsevier, 2006) Ayodele, A. E.; Olowokudejo, J. D.
    Comparative studies have been carried out on the leaf epidermal features of the species in the family Polygonaeae in West Africa. Epidermal cells are mainly isodiametric in Symmeria paniculata, irregular or more often polygonal with curved, straight and undulate to sinuate anticlinal walls. A few species e.g. Polygonum plebeium, Oxygonum sinuatum, Persicaria nepalensis and Harpagocarpus snowdenii have striations on their epidermal walls. All species except Afrobrunnichia erecta and H. snowdenii are amphistomatic and the family is characterized by a wide range of stomata types such as the anisocytic in P. plebeium, cyclocytic in S. paniculata and a few Persicaria, anomocytic, diacytic, parallelocytic and paracytic which is regarded as the basic type for the family based on its widest occurrence among the species. However, different stomata types may occur on the same leaf surface. The unicellular, or multicellular, uniseriate aggregated trichomes are significant in the recognition of taxa in the Persicaria except in P. senegalensis forma albotomentosa which has short uniseriate flagelliform trichomes. The significance of these observations is discussed in relation to the taxonomy of the family.