Chromosome Aberrations in Spinifes littoreus from the Monazite Belt at Manavalakurichi

Abstract

Cytology of four clones of S. littoreus from 3 different radiation levels at the monazite area at Manavalakurichi and one from Kovalam, a nonmonazite area was examined. The plants from Kovalam showed 9 bivalents in PMCs and 18 chromo-somes in root tip cells. The clones I and II from Manavalakurichi showed very high frequency of PMCs with interchange configurations and clones III and IV showed very low frequency of a ring of four chromosomes and fragments in PMCs. Analysis of the translocation configurations and their frequency in clones I and II has revealed that there are at least 3 translocations of long standing in each of them, in two of which a single homologous pair of chromosomes is involved. It is shown that one of the interchanges is either common to clones I and II or at least involve exchanges of almost equal sized segments between the same chromosomes. The occurrence of a low percentage of quadrivalents in clones III and IV is suggested to be the result of interchanges occurring in microsporocytes in these plants. The chromosome breaks prior to the formation of these interchanges and fragments in the PMCs in clones III and IV are suggested to be induced by natural radiations from monazite. The translocations of long standing in clones I and II are also shown have occurred as a result of natural radiations in these long established species. The occurrence of these chromosome aberrations in S. littoreus alone of all the plant species in this area and its persistence is attributed to its creeping growth habit and capacity for vegetative propagation.