CYTOMORPHOLOGICAL STUDIES OF SOME NIGERIAN ASTERACEAE- TRIBE SENECIONEAE

Abstract

Cytological and morphological studies have so far been carried out on 32 taxa belonging to 19 species and 5 genera of members of the tribe Senecioneae (Asteraceae) from Nigeria. The report of 12 taxa belonging to 10 species and 4 genera are presented in this study. Pollen fertility test of the species studied revealed that meiosis was normal with regular bivalent pairing thus the plants were stable. Chromosome count of 4 species Gynura miniata (n=5), Senecio baberka (n=5), Senecio lelyi (n=10) and S. manni (n=10) are reported for the first time from the Nigerian flora. The presence of 2 cytotypes of Emilia praetermissa, (n=10) and (n = 12) is reported for the first time in the genus. Achene morphology of all the species studied has been drawn and described for the first time. The distribution maps of all the taxa studied have been provided for the first time and they revealed members of the tribe are prevalent at higher altitudes. There is no correlation between chromosome number and annual habit or between achene morphology and growth habit. Base number of 5 has been suggested for the tribe and a probable pathway of the evolution of the Nigerian Senecioneae has been suggested. The report of Gaillardia pulchella Foug an introduced plant is reported for the first time from our flora