Cyto-genetical Studies on Tricyrtis, IV

Abstract

1) One hybrid (2n=26) of Tricyrtis hirta and T. formosana has three short SAT-chromosomes and an amphidibasic plant (2n=52) induced from this hybrid by the colchicine method has six short SAT-chromosomes. Another hybrid (2n=25) of the same parental species has two long and three short SAT-chromosomes and clearly shows absence of one short chromosome. The number of SAT-chromosomes in these plants corresponds to the maximum number of nucleoli at telophase.2) The basikaryotype analysis in the 26-chromosome hybrid clearly showed partial homology in three short and one long chromosomes and these partially homologous chromosomes were sometimes remained as univalents which were six in maximum number (cf. table 1). Small inversions of long and short chromosomes were analyzed by the presence of chromatid bridges.3) The basikaryotype analysis in the 25-chromosome hybrid clearly showed absence of one partially homologous chromosome found in the 26-chromosome hybrid. Univalent chromosomes varied from one to five in the former hybrid (cf. table 4). Chromatid bridges and fragments were also observed and longitudinal split of the univalent chromosomes was rarely observed in the first meiotic anaphase.4) The hypothesis of pairing block has been advanced to explain the pairing of partially homologous chromosomes.5) Differential amphiplasty (disappearance of satellites) and mobilization of the nucleolar chromosomes of terminal type were described.The present work was aided by a grant from the Japan Society for the Advancement of Cytology, to which the writers wish to express their best thanks.