The Pollen Morphology of the genus Polygonum s.str.(Polygonaceae)in China and its Classific Significance

The pollen morphology of 13 species,1 varieties and 1 forma of the genus Polygonum s.str.(Polygonaceae)in China were examined through the scanning electron microscope(SEM).The results show the pollen grains prolate or perprolate,tricolporate,but exine ornamentations are sharply various and may be divided into 4 types:(1)Pollen surface finely reticulate;(2)Pollen surface granulate;(3)Pollen surface granulate merely on the shoulders of mescolpium,but smooth all the rest;(4)Pollen surface smooth on the shoulders of mescolpium,but granulate all the rest.Basing on the pollen morphological features and the habit,petioles and pedicels articulate or not,number of the styles and stigmata and shape of achenes as well,the authors propose a four sectional classification of the genus Polygonum s.str.in China:(1)Section Fruticulosae(Boiss.)F.Z.Li et Y.T.Hou,stat.& comb.nov.;(2)Section Polygonum;(3)Section Pseudomollia Boiss.;(4)Section Plebeia Tzvel.