Pollen Morphology of Nine Chinese Species of Uncaria Schreb. (Rubiaceae)

Abstract:

Pollen morphology of nine Chinese species of Uncaria Schreb. was observed using scanning electron microscopy (SEM) and light microscopy (LM). The pollen grains are monad, small, radically symmetrical, and tricolporate, with a spheroidal to subprolate shape in equatorial view and three-lobed circular shape in the polar view. The ectocolpus is crack-like up to poles. A protruding oncus is often found in the middle of the ectocolpus. The exine ornamentation is striate to microreticulate, and without supratectal element. The genus Uncaria is fairly stenopalynous, because of a lack of variation of pollen characteristics at species level. The pollen morphology of Uncaria belongs to plesiomorphic type in Rubiaceae.

Key words:Uncaria; Pollen morphology; China