Correlation between ethyl methanesulfonate uptake by barley embryos under different treatment conditions and mutation frequency
Khalatkar, A.S.; Gopal-Ayengar, A.R.; Bhatia, C.R.
Mutation Research 43(1): 45-55
Uptake of ethyl methanesulfonate [EMS] and its alkylation in the TCA[trichloroacetic acid]-insoluble fraction of embryo cell lysates was followed after hull-less barley seeds (karyopses) were treated with 3H-labeled EMS. The effects of modifying factors such as pre-soaking of seeds in water before mutagen treatment, post-soaking and drying after treatment were investigated. The effects of the same factors on M1 [1st mutation generation] parameters and chlorophyll mutation frequencies in the M2 [2nd mutation generation] were studied in parallel experiments with cold EMS. The uptake of EMS on the dry matter basis was greater in the embryo than in the rest of the karyopses. Movement of the mutagen or its hydrolytic products into the embryo from seed endosperm was noted during germination. Enhanced mutation frequencies in M2, when pre-soaked seeds were treated, was partly due to greater uptake of mutagen. The mutagen and its hydrolytic products were leached out of the treated seeds during the post-soaking. Leaching decreased the effect on M1 parameters but had no significant effect on mutation frequencies in the M2. Drying of seeds after treatment with the mutagen and storage for 7 days increased alkylation in the TCA-insoluble fraction and enhanced mutagenic and deleterious effects. At least some of the differences in mutation frequencies after various treatment procedures were due to variation in the actual dose of the mutagen ultimately received by the target cells.