Pollen morphology and its systematic significance in zanthoxylum (rutaceae) from china

Pollen grains of 32 species of Zanthoxylum were studied under light microscopy and scanning electron microscopy. The macro- and micro-morphological pollen characters, including shape, pollen size, aperture and exine ornamentation type were examined. The pollen grains are small to medium in size, mostly from subspheroidal to prolate shape in equatorial view and 3-lobed circular in polar view. Three types are recognized based on exine ornamentation, includes macroreticulate, parallel striation, and striate-rugulate. Pollen shape and size are found to have only minor value, but pollen exine ornamentation contains useful information on modify the Englerian classification of Zanthoxylum and can be used for identifying different species of Zanthoxylum s.l.. Based on the pollen morphological data, the two subgenus, Fagara and Zanthoxylum, should be combined. (author)