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

Abstract

Counts of spikes showed that the frequency of mutations induced in barley by ethyl- or methyl-methanesulfonate was affected by the pH of solutions, by presoaking seeds in water and by post-treatment conditions (soil moisture and soil temperature). Plants grown from seeds treated at 30[degree]C had many more mutations than those from seeds treated at 20[degree]C (e.g. 38.8% vs 27.9% of spikes). The mutation-inducing sequence in cells is started during or immediately after the chemical treatment. In H3-thymidine-treated embryos DNA replication occurs within 6 hr. of wetting in some root-meristem cells. Early mitoses are unlabelled indicating that some root-cells of the dormant embryo are 2C, others 4C. In the shoot apex no mitoses occurred in the first 24 hr. of germination. All mitotic figures to 60 hr. were unlabelled. Shoot-apex nuclei thus appear to be predominantly 4C.