POLLEN STUDIES ON FOUR SPECIES OF CRASSOCEPHALUM (MOENCH.) S. MOORE (ASTERACEAE) IN SOUTHWESTERN NIGERIA

Twenty-three accessions of four species of the genus Crassocephalum were investigated on their pollen size, pollen morphological structure and fertility. Pollen sizes were obtained from polar and equatorial diameter measurements. Pollen fertility was accessed through the staining property in cotton blue in lactophenol reagent. The structural form of pollen grains was examined by means of a light microscope (X100 magnification). There was no significant difference in pollen size, structure and fertility among species investigated. C. crepidioides had relatively the largest size of pollen grains (28.10±1.67 µm) (media), while C. rubens pollen were relatively most fertile (98.7%). However, pollen grains of the species were tricolporate with three germ pores except in C. crepidioides which had up to six germ pores (multiporate). All pollens in the species were fenestrate type with high fertility. The study suggests that number of germ pores in addition to pollen morphology be used in species separation