Comparative Morphological and Palynological Studies on Some Species Of Sida L (Malvaceae) in Nigeria

Abstract A comparative morphological and palynological study was conducted on eight Sida species in Nigeria to identify diagnostic characters for their accurate identification and classification. Qualitative and quantitative vegetative, floral, and pollen characters were evaluated using standard taxonomic procedures. Pollen grains were acetolysed and examined under a light microscope, while hierarchical cluster analysis was employed to assess species relationships based on morphological and palynological characters. Morphological observations showed that all species possessed simple leaves that varied in shape from linear-lanceolate, cordate, oval, and rhomboid to acute and acuminate, with leaf surfaces either pubescent or glabrous. Inflorescences were solitary and axillary or arranged in clusters, while petals were consistently five, connate, and varied in colour from white (S. linifolia) and pale orange (S. urens) to yellow in the remaining species. All species produced dehiscent fruits. Palynological analysis revealed that all pollen grains were large and oblate-spheroidal. The polar axis ranged from 70.00 ± 3.54 µm in S. acuta to 153.75 ± 12.37 µm in S. pilosa, whereas exine thickness varied from 9.75 ± 0.35 µm in S. urens to 15.00 ± 0.35 µm in S. rhombifolia. Pore number and pore diameter also varied considerably among the species. Cluster analysis grouped morphologically similar taxa, with S. pilosa,S. urens, S. alba,S. corymbosa, and S. acuta,S. rhombifolia showing close affinities, while S. linifolia formed a distinct cluster. Therefore morphological and pollen morphological data provide diagnostic information for differentiating Sida linifolia, Sida pilosa, Sida urens, Sida acuta, Sida alba, Sida cordifoli, Sida corymbosa, Sida rhombifolia.Keywords:Sida, morphology; palynology; pollen morphology; hierarchical cluster analysis.