Abstract
The thesis consists of two parts. Part I contains
a meiosis-based cytogenetic survey of 16 commonly occurring Composites of Bangladesh. These species belong to
14 genera and seven tribes. This study mainly includes
the determination of basic and haploid chromosome numbers,
chromosome association, ploidy level, mean chiasma frequency per bivalent and average chromatin surface area of
the bivalents, for all these species. No correlation has
been found between the mean chiasma frequency per bivalent
and mean chromatin surface area per bivalents, and thereby,
it is concluded that chiasma formation does not depend
upon the size of the bivalents.
Part II is an experimental study of two Composites,
Chrysanthemum carinatum Schousb. and Tridax procumbens L.
The former was a reciprocal translocation heterozygote.
Nature and orientation of its interchange complexes have
been studied. It is concluded that the type of such orientations is, probably, determined by the genotype of the
organism rather than by the physical properties (length,
centromere poșition, localisation of chiasmata etc.) of its chromasomes. The latter, Tridax procumbens L., was
irradiated in an attempt to induce reciprocal translocation. However, translocation could not be induced
although, among other features a sharp decline in the
chiasma frequency was observed. In the next generation
there was a slight rise in the chiasma frequency indicating that partial recovery is possible after radiation
effect