EFFECTS OF SOME VARIATIONS OF TREATMENT-METHODS ON MUTATION FREQUENCY IN BARLEY TREATED WITH SOME MONOFUNCTIONAL ALKYLATING AGENTS

Introduction When a chemical mutagen such as ethyl methanesulfonate (EMS) or ethyleneimine (EI) is applied, in solution, to barley grains, the frequency of mutations induced depends on dose, (concentration X time), temperature and other factors. W e have been interested in determining what modifications of mutation frequencies are brought about by varying the treatments given. Many of our tests have involved EMS but in some experiments methyl methanesulfonate (MMS) or EI were used. All three of these compounds are monofunctional alkylating agents. Results are reported here for mutation frequencies recorded after (1) treating different seed lots in identical fashion at different times; (2) varying the dose; ( 3 ) presoalting seeds for some hours prior to applying the mutagen; (4) varying the p H of chemical solutions; (5) varying temperature during treatment. Observations have been made also on the time at which D N A synthesis begins in different parts of embryos aroused from the dormant condition and the time at which mitosis begins in embryos of germinating seeds (a) on filter papers moistened continuously with water and (b) on moist filter paper after a 2-hour exposure to a solution of EI. Earlier reports on the effect of some variations in treatment methods with alltylating agents have been given by Heslot e t (11. (1959), Ehrenberg et 01. ( 196 1 ) , Froese-Gertzen e t nl ( 1961), Konzalc e t (11 ( 1965), Arnason and Minocha (1965), Ramanna and Natarajan (1966), and others. The accumulation of information on this subject should be useful when attempts are made to unravel the mechanisms of action of the mutagens in the production of mutations.