Abstract
Dioscorea alata L. has three stomatal complex types, namely, paracytic, anisocytic, and tetracytic stomata, with percentage frequency values of 50, 18, and 32, respectively. Dioscorea bulbifera has paracytic and anisocytic stomata, with percentage frequency values of 87.60 and 12.40, respectively. Dioscorea cayenensis has anisocytic stomata, with a percent?age frequency value of 100. Dioscorea dumetorum has tetracytic and paractytic stomata, with percentage frequency values of 91.05 and 8.95, respectively. Both D. esculenta and D. rotundata have paracytic stomata, with a percentage frequency of 100. The range of variation of stomatal density is from 10 (lowest value) in D. alata and D. dumentorum to 27 (highest value) in D. bulbifera. The stomatal index also varies, from 24 in D. alata to 47 in D. cayenensis. The size of stomata in all species is small, varying in length from 0.74 ?m in D. alata to 1.79 ?m in D. dumentorum. An indented dichotomous key based on stomatal features was constructed to distinguish and identify the species.
Highlights
The yams, Dioscorea L. of the family Dioscoreaceae, are monocotyledonous tropical plants which produce underground or aerial tubers and are cultivated on a wide scale in West Africa, the Carribbean and Southeast Asia as a major source of calories for the peoples of these tropical areas (Ikediobi and Igboanusi, 1983)
Fresh specimens were collected from the Grain Research Unit (GRU) of the International Institute of Tropical Agriculture (IITA), Ibadan
Specimens were identified at the Herbarium of the Department of Plant Biology, University of Ilorin, Ilorin, Nigeria
Summary
The yams, Dioscorea L. of the family Dioscoreaceae, are monocotyledonous tropical plants which produce underground or aerial tubers and are cultivated on a wide scale in West Africa, the Carribbean and Southeast Asia as a major source of calories for the peoples of these tropical areas (Ikediobi and Igboanusi, 1983). Yam is the common name applied to plants of about 500 species (Stephens, 2003) or 600 species (Milne-Redhead, 1975; Okeke, 2001) of the genus Dioscorea. Of the 20 species of the genus Dioscorea recorded for West Tropical Africa (Miege, 1968), only D. burkilliana J. D. lecardii De. Wild, and D. sagittifolia Pax have not been recorded for Nigeria. The species under cultivation in Nigeria include D. alata L., D. bulbifera L., D. cayenensis Lam., D. dumetorum (Knuth) Pax, D. esculenta (Lour.) Burkill, and D. rotundata Poir. The present study attempts to address this issue This is with a view to providing baseline data that may be useful for further studies on the genus
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