Abstract

DE GUERRA, Nilda Alcorcés; LAREZ R, América  and  MAYZ F, Juliana. Additions to the cytogenetic knowledge of Tithonia diversifolia (Hemsl.) A. Gray (Asteraceae). Acta Bot. Venez. [online]. 2007, vol.30, n.2, pp.267-275. ISSN 0084-5906.

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.

Keywords : Chromosomes; Cytogenetic; Meiosis; Microsporogenesis; Mitosis; Tithonia diversifolia.