Pollen micromorphology of selected Caesalpinioideae taxa and its taxonomic role

This study presented the pollen micromorphology of some Caesalpinioideae species sampled from different geographical regions of Hainan Island south China and Pakistan and observed under scanning electron microscope (SEM). The multivariate principal component analysis (PCA) was performed by using five variables to show the relationship among the species. The results showed that heteromorphy in pollen features; i.e., small and large size pollen, outline (circular, triangular, elliptical), shape (spheroidal, sub-spheroidal, oblate, prolate), detail of the apocolpium region (small, large), type of endoapertures and exine sculpturing (reticulate, finely reticulate, macro-reticulate, perforate, psilate) can help significantly in the discrimination of taxa. The PC-1 showed significant variation (60.06%) while the PC-2 (20.90%) variation between the species. The correlation coefficient calculated among the pollen traits indicated that there were positive and significant correlations between the polar and equatorial axis indicating similarity in shape in most of the taxa. The quantitative data together with the qualitative characteristics assist in the delimitation of species within the subfamily. Hence, our study contributes to confirming the eurypalynous characteristics of the Caesalpinioideae.