Pollen morphology and its systematic implications for the generaKeiskea miq. andCollinsonia L. (Elsholtzieae-Lamiaceae)

摘要

The pollen morphology of six species ofKeiskea and three representative taxa ofCollinsonia was studied in detail using LM, SEM, and TEM. In both genera, pollen grains are monad, hexa-colpate, and mostly medium in size [P = 28.0 to 37.0 μm, E = 24.3 to 30.7 μm (Keiskea); P = 30.0 to 45.0 μm, E = 26.0 to 39.0 μm (Collinsonia)]. Polar outlines are of circular or ellipsoid form. Shapes range from primarily oblate-spheroidal to prolate-spheroidal to subprolate, and rarely prolate in the equatorial view. Their exine, including the inline characters, are clearly distinct from each other:Keiskea, well-developed bi-reticulate, often forming large lumina by supratectal ridges, unbranched columellae, one-third to one-half of the total exine thickness; versusCollinsonia, mostly perforate without supratectal ridges or a faint/very weak bi-reticulate appearance without supratectal ridges, seemingly branched columellae, ca. two-thirds of the total exine thickness. As demonstrated by these current data, the pollen morphology of the two genera is well distinguished, easily supporting the separation ofKeiskea fromCollinsonia.