Pollen Studies On Some Species Of Didymocarpus Wall. And Related Allies In Gesneriaceae

Pollen morphology of ten species and one variety of Didymocarpus Wall. and related allies ( Gesneriaceae ) were studied by scanning eletron microscope ( SEM ). The ornamentations can be devided into three different groups. First, finely reticulate, including Didymocarpus hancei, D. Salviiflorus, Chiritopsis xiuningensis, Gyrocheilos microtrichum and G. retroichum var. Oligolobum. Second ,coarsely reticulate, including D.primulifolius, D. aromaticus, D. praeteritus and D. purpureobracteatus. Third, tuberculate, only one species G. chorisepalum. The pollen grains of genus Didymocarpus are tricolporoidate, prolate spheroidal or subprolate in shape, lobate-circular in polar view. The size of the pollen grains is (14.6~20.3)16.3×14.4(12.7~16.5)μm.The colpi reach as far as the pole, wide and with some granular processes more or less. The ornamentation are reticulate or finely reticulate. The pollen grains of genus Gyrocheilos W. T. Wang are tricolporoidate, prolate spheroidal in shape, lobate-circular in polar view. The size of the pollen grains is (12.9~13.8)13.3×12.0(11.0~12.9)μm. Colpi reach as far as the pole and narrow. The ornamentation are finely reticulate or tuberculate. The pollen grains of genus Chiritopsis W. T. Wang are tricolporoidate, prolate spheroidal in shape, lobate-circular in polar view. The size of the pollen grains is (12.1~15.9)13.9×14.3(12.5~16.4)μm. Colpi reach as far as the pole, constricted in the middle, narrow and with some granular processes. The ornamentation are finely reticulate, with coarse muri. The lumina are very small , circular or subcircular in the shape. The pollen grains of genus Dolicholoma D. Fang et W. T. Wang are tricolporoidate, prolate spheroidal in shape, lobate-circular in polar view, subcircular in equatorial view. The size of the pollen grains is (19.3~20.0)19.6×19.2(18.7~19.7)μm.The colpi are short and narrow, with some granular processes. The ornamentation are reticulate, with narrow, smooth muri and irregular lumina.For the sake of convenience, we compared the pollen morphology data of genus Chirita Buch.-Ham. ex D. Don and genus Calcareoboea C. Y.Wu ex H. W. Li reported. The result of pollen morphology tends to support the treatment of taking Sect. Heteroboea, including D. hancei and D. salviiflorus out of Didymocarpus. But our result don't support The treatment of removing D. hancei from Didymocarpus Wall. and categorize to the genus Calcareoboea. The opinion of demoting genus Gyrocheilos to beneath Didymocarpus sect. Didymocarpus don't get the support of pollen morphology materials.