Cytogenetic analysis of Lathyrus japonicus willd. (Leguminosae)

L. japonicus belongs to section Orobus and grows in most of the seashores o f the Northern Hemisphere and as adventitious in Chile. In this report a de tailed analysis of karyotype and meiotic behaviour was carried out in order to provide data for phylogenetic analysis. This species presented a symmet rical karyotype with 2n=14, 6m+8sm chromosomes. The longest and the short e st chromosomes of the complement were metacentrics while the sm were very s imilar and medium in size. NORs, determined by argentic staining, were loca lised in secondary constriction of the long arm of the longest m chromosome . The symmetrical karyotype is in accordance with the ancestral morphologic al characters showed by L. japonicus. Meiotic behaviour was regular with a chiasma frequency of 2.5 per bivalent at metaphase I. This fact agrees with the 98.2% of pollen stainability estimation. However, in ana-telophase I a bridge and fragment (<1%) were observed, while in interphase only fragment s were detected (1%). In addition, out of plate chromosomes appeared in met aphase I and II (2%). These chromosomes segregated independently, formed mi cronuclei in telophase II and they became micromicrospores at the tetrad st age. These micromicrospores correspond to the micro pollen grains observed in anthesis.