Pollen morphology and chromosome number of Vernonia rojasii (Vernonieae, Asteraceae)
Swedish Museum of Natural History
Lugar: Stockholm; Año: 2001 vol. 36 p. 69 - 76
Pollen morphology and chromosome number are reported for the first time in Vernonia rojasii Cabrera, an endemic species from central Paraguay. The species presents a somatic chromosome number of 2n=4x=36, with the karyotype mostly composed by telocentric chromosomes. Pollen grains of V. rojasii are triporate, lophate, semitectate, with smooth crests on the muri. This pollen type has been previously called E and it is mostly present in Old World species of Vernonia. The basic chromosome number x=9 found in V. rojasii also indicates a probable close relationship with species of Africa and Asia, when this constitutes the more frequent number. In the meanwhile, almost all the American species have different types of tricolporate pollen which has been designated A, B, C and D and present basic chromosome numbers that varies from x=10 to x=19.