Adiciones al conocimiento citogenético de tithonia diversifolia (HEMSL.) A. gray (asteraceae)

with the objective of corroborating the chromosomal number, the pollen size, type and viability, in a study of the meiosis of tithonia diversifolia, meristematic root tips treated with colchicine (0,05%) and young inflorescence anthers, collected from different localities of monagas state, venezuela, were studied. a diploid chromosome number (2n = 34) was found,with 16 metacentric pairs and one submetacentric pair. lagging chromosomes in me-taphase i and anaphase i, and asynchrony in metaphase ii were observed. spermatic nuclei could not be seen in 65% of pollen grains. abnormalities which may be associated with the low pollen fertility (35%) were detected in this species. pollen grains were of triporate type and had muricate sculpture, with an average size of 26.5 mm. the microsporogenesis was of the simultaneous type.