Pollen morphological study of four species of Talinum genus (Portulacaceae) occurring in Ondo and Ogun States Southwestern Nigeria

Pollen morphology plays a critical role in resolving taxonomic ambiguities among closely related plant species. This study investigated the palynological characteristics of four Talinum species (Talinum fruticosum, Talinum paniculatum, Talinum portulacifolium, and Talinum triangulare) occurring in two States found in South-western Nigeria. The aim is to identify diagnostic traits that will accurately delineate the species palynologically. Flower buds were crushed and processed for acetolysis. Light microscopy was used to observe and measure key pollen traits. The pollen were monads, spheroidal, isopolar, and radially symmetrical with columellate exine ornamentation. Pollen was pantoporate having 30–40 pores in three species except for T. paniculatum with pantocolpate grains. Quantitative characters showed significant differences in pollen size and exine thickness. Talinum fruticosum had the largest polar axis (57.20 ± 0.23 µm) and equatorial diameter (57.50 ± 0.22 µm), while T. paniculatum fell into media class, (40.50 ± 0.33 µm and 40.85 ± 0.33 µm while the other three species fell into magna class. Exine thickness varied significantly; Talinum triangulare exhibited the thickest walls (2.78 ± 0.04 µm) and T. paniculatum the thinnest (1.85 ± 0.02 µm). Pearson correlation analysis showed positive associations between polar and equatorial axes (r = 0.98) and between colpus length and width (r = 0.98). Notably, negative correlations were observed between colpus traits and pore dimensions. Hierarchical clustering showed that T. triangulare and T. portulacifolium are closely related followed by T. fruticosum while T. paniculatum formed a separate branch. Aperture type, exine thickness, and grain size emerged as robust diagnostic traits. The distinctiveness of T. paniculatum suggested its potential status as a morphologically divergent when compared to other species.