Modification of Relative Mutagenic Efficiency in Barley of Mesyloxy Esters by Different Treatments

Abstract

THE mutagenicity of mesyloxy esters of differing chemical structure has been studied in Drosophila, and the marked differences observed have been attributed to differences in the reactive alkyl group and the non-alkylating “prosthetic” parts of the compounds¹. Relationships between the chemical structure and the biological effects of different monomesylates have also been studied in barley². Although the qualitative and the quantitative differences in the biological effects, including chromosome breakage and mutation rates, produced by this group of compounds have been attributed to a correlation between structure and activity, very little attention has been paid to the physical factors which may influence the reactivity. By “physical” we mean such factors as temperature and hydrogen ion concentration of the treatment solutions, which may influence the reactivity, functionality, stability and the rate of diffusion of a chemical, and which in turn may modify its biological effects. We have therefore studied the modifying effects in barley of temperature and hydrogen ion concentration on various biological effects produced by the three mesyloxy esters—ethyl methane-sulphonate (EMS), methyl methane-sulphonate (MMS) and 1,4-dimethylsulphonoxybutane (myleran). The compounds have different reactive alkyl groups. The present report summarizes data relating to the effect of temperature and pH on the frequency of chromosome breakage in somatic cells and on chlorophyll mutation rates induced in barley by the three chemicals.