Pollen Morphological Characteristics of 46 Germplasm Resources of Polygonatum and Its Taxonomic Implications

To elucidate the morphological diversity and genetic characteristics of the pollen of <i>Polygonatum</i> species, this study utilized a total of 46 samples encompassing six species and one variety of <i>Polygonatum</i>. Scanning electron microscopy (SEM) was employed to examine the morphological traits of the pollen and to analyze the evolutionary patterns and genetic relationships among <i>Polygonatum</i> species. The results indicate that the pollen grains of the 46 <i>Polygonatum</i> germplasm are uniformly characterized as monads, heteropolar, bilaterally symmetrical, atreme, and possess a mono-sulcus. They were peroblate (P/E-ratio = 0.36-0.42) in shape and medium to large (P = 18.17-27.15 μm, E = 44.11-67.07 μm) in size. And there are four types of exine ornamentation: reticulate, reticulate-perforate, reticulate-rugulate, and reticulate-verrucate. The 46 germplasm resources were classified into four clusters based on the results of a pollen morphology clustering analysis: <i>P. cyrtonema</i> and <i>P. macropodum</i> were grouped into cluster I, <i>P. filipes</i> and <i>P. odoratum</i> into cluster II, <i>P. kingianum</i> and <i>P. kingianum</i> var. <i>grandifolium</i> into cluster III, and <i>P. alternicirrhosum</i> was classified as cluster IV, standing alone. This study tentatively suggests that pollen morphology, particularly pollen size and exine ornamentation, can serve as a valuable reference for the classification, genetic relationship, and evolutionary patterns of the genus <i>Polygonatum.</i>