Meiosis and pollen grain development in Isolepis cernua f. cernua (Cyperaceae)

In this paper, cytogenetic studies and pollen grain development of Isolepis cernua (Vahl) Roem. & Schult. f. cernua (Cyperaceae) from Argentina are pr esented. The somatic chromosome number found is 2n = 54, being different fr om previous reports. Primary constrictions have not been observed, suggesti ng that they are holocentric chromosomes, as in many species of the family. The meiotic behaviour was described showing n = 27 and axial orientation o f some of the bivalents. Three of four pollen nuclei degenerate while one o f them completes the mitosis. These processes originate the pseudomonad, a characteristic feature in the Cyperaceae. This fact does not affect the pol len fertility which is 98%.