Tetraploid PMCs of Rhoeo induced by low temperature treatment

Abstract

In the winter of 1937, pots of Rhoeo discolor Hance were transfered from the green house (23°C) to the place of 2°C for four hours and then were put back again. Two weeks after treatment, some anthers were found to contain a considerable number of tetraploid PMCs mixed among the normal diploid ones. The chromosome configurations were studied by one 'diakinesis' (Fig. 6) and nine MI (Figs. 2-4 and 7-15) PMCs. They involved univalents, ring bivalents, chains of three or more chromosomes, rings of 4 chromosomes and polyvalents bearing triple terminal chiasmata. They are all similar to those demonstrated by Seitz (1935) in tetraploid Oenothera species. These 4x-PMCs are ascribed to be due to the failure of cytokinesis at the last mitosis in the archesporial tissues which were affected by influence of low temperature treatments. The chromosome configurations observed favor the assumption that Rhoeo is an interchange heterozygote as has been hitherto inferred only from ring configurations.