Phenological Study of Some Herbaceous Species of Euphorbia l. (Euphorbiaceae l.) in Nigeria

The phenological study provides a detailed comparison of life cycles of six species of Euphorbia with a view to enhancing the knowledge of the taxonomic status of the genus. Growth and developmental stages were investigated using pot experiments. Description of six principal growth stages was done and these include leaf development, shoot development, flowering emergence, fruit development, seed ripening and seed dispersal. All the investigations were carried out for 77 days under the same experimental conditions. Germination of all species started 24 hours after sowing indicating that their seeds have physiological capacity to readily germinate owing to their absence of seed dormancy. The life cycles from seed germination to seed dispersal are determined to span between 72-73 days in E. graminea, 62-65 days in E. heterophylla, 66-68 days in E. hyssopifolia, 62-63 days in E. hirta, 46-48 days in E. prostrata and 70-72 days in E. thymifolia. All data were recorded and thereafter subjected to appropriate statistical analysis. Variations are observed in the germination behaviour, seed output and reproductive capacity among the species. Flowering, fruiting and seed production dropped because of the presence of early cyathium abortion which is characterised by enlarged ovaries without seed development, it was high in E. hirta and low in E. thymifolia. A new identification key to the Euphorbia species is included.