Pollen Morphological Peculiarities of Selected Mimosoideae Taxa of Hainan Island and Their Taxonomic Relevance

Abstract

Mimosoideae is one of the taxonomically complex subfamilies of Fabaceae. Several studies have reported the pollen morphology of Mimosoideae taxa and their taxonomic relevance, but no such study was found specifically for Hainan Island in southern China. Therefore, the present study was designed to investigate the selected Mimosoideae taxa and explore the new palynological traits to support and strengthen the systematics of Mimosoideae using multiple microscopic techniques. The polar axis, equatorial diameter of the pollen grains, colpus length and width were measured. The smallest pollen grain size was found in Mimosa pudica (7.8 × 7.75 µm), while the largest pollen size was found in Albizia lebback (87.54 × 77.97 µm). Similarly, significant variation was found in the exine and colpus surface patterns. The subfamily Mimosoideae is considered eurypalynous because of the variation in pollen traits. In addition, variation was also found in the quantitative traits. Comparatively, the pollen features were found to be helpful at the genus and species levels, as well as in the correct identification and discrimination of the taxa. Hence, this study gives a detailed account of the pollen morphologies of certain selected taxa of Mimosoideae collected from different geographical regions on Hainan Island. The pollen morphological traits were proven to have significant taxonomic potential and can be used as additional tools for the correct identification and discrimination of Mimosoideae taxa. These results will provide the basis for further systematic studies.