Palynology of the genera of Cactaceae Maihuenia (Maihuenioideae) and Pereskia (Pereskioideae) from Argentina

Pollen grains of five species from two genera of the subfamilies Maihuenioideae andPereskioideae (Cactaceae) are described with the optical and scanning microscopes.Maihuenia (F.A.C.Weber) K.Schum.: M. patagonica (Phil.) Britton & Rose and M. poeppigii(Otto ex Pfeiff.) F.A.C. Weber ex K. Schum. (Maihuenioideae) and Pereskia Mill.: P. aculeataMill., P. nemorosa Rojas Acosta and P. sacharosa Griseb. (Pereskioideae). The studied pollengrains of genera Maihuenia are prolate or spheroidal, medium or large sized, and Pereskia areall spheroidal and large sized. The apertures show variation in number: three to fourteen,colpate, with different pattern distribution and length of the colpus: Maihuenia has tricolpategrains and Pereskia 6-14 pantocolpate, some of them form syncolpos. The sculpture does notshow marked differences between the species, which is microechinate and nanoechinate withperforations surrounded by a thickening. A key to determine the species of each genus ispresented