Pollen morphology of Callicarpa L. (Lamiaceae) from China and its systematic implications

Pollen morphology of 36 species and 9 varieties of Callicarpa L. (Lamiaceae) from China was investigated through scanning electron microscopy. Pollen grains of the genus are monads, radiosymmetric and tricolpate, mainly medium in size, spheroidal (rarely subprolate, prolate or suboblate) in equatorial view and (sub) circular or rounded triangular in polar view. The edge of colpus is thin, perforate or thickened but imperforate and the colpus membrane of the investigated taxa is usually uneven (sunken or raised), with finely/coarsely granular or irregular striation. Four different ornamentation types are delimited on the basis of exine sculpturing: (1) coarsely reticulate; (2) microreticulate; (3) rugosely reticulate and (4) rugulate reticulate. The results do not support the traditional infrageneric classification of Callicarpa which is based on stamen characters. However, pollen characters provide evidence to support Callicarpa as the sister to the Australian subfamily Prostantheroideae, a relationship previously suggested by molecular phylogenetic analyses.