Chromosome Studies an <i>Trillium kamtschaticum</i> Pall

Abstract

1) The subjection of Trillium plants to high temperature prior to the meiotic divisions has produced several abnormalities upon meiotic chromosomes which were distinguishable into two categories, (i) concordant and (ii) discordant.2) The concordant anomalies are dependent upon the balanced acceleration rates of the behavior of the kinetochore and of the rest of chromonemata. They are different from the control merely in the dimensions of chromosomes and of entire mother-cells, but quite normal in the mode of bivalent formation and the subsequent behavior of chromosomes.3) The discordant anomalies are dependent upon the upsets in timing relationships between the kinetochore and the other pari of the chromonemata. The consequences are (i) the occurrence of 10 univalents at the first metaphase, which is due to either (a) complete failure of synapsis (asynapsis) or (b) premature separation of the associated kinetochores (desynapsis) and (ii) the occurrence of 10 ‘dyads’ each consisting of two separated chromatids lying parallel (‘precocious-a’) or 5 ‘tetrads’ each consisting of four chromatids associating in cruciferous forms (‘precocious-b’). These are illustrated in Diagram 1.4) The significances of the kinetochore in the meiotic divisions are discussed in connection with the relationship between mitosis and meiosis and wich the forces acting upon the kinetochore at metaphase.