Pollen morphology of Oxalis species from Buenos Aires province (Argentina).

Pollen morphology and the degree of pollen variability within nine species and two varieties of Oxalis species from Buenos Aires Province (Argentina) were studied using light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Oxalis pollen grain is generally 3-colpate and the shape is prolate spheroidal, oblate spheroidal or spheroidal. The exine is microreticulate. The brochi are circular to polygonal; brochi sizes decrease near the colpi. The colpus membrane observed in unacetolysed material, is crustate or granular. The colpus length varies within a species; the largest grains are produced in stamens with long filaments and the smallest ones in stamens with short filaments. Four pollen types are distinguished by means of LM, SEM and TEM. They are recognized mostly on the basis of their colpus membrane structure. In conclusion, the morphological similarity among Oxalis species is also reflected in their pollen morphology.