Pre-replication recovery from induced chromosomal damage

Barley seeds were treated with diethyl sulphate (DES) or methyl methane-sulphonate (MMS) and stored at 30% water content for 3–28 days, i.e. under conditions artificially prolonging the period between the mutagenic treatment and the onset of DNA synthesis and favourable for the repair of induced DNA single-strand breaks. Storage of seed led to a marked decrease in the frequency of induced chromosomal structural changes (aberrant metaphases) as compared with treatments without storage. The recovery involved mainly chromatid-type aberrations, whereas chromosome-type aberrations induced by MMS were recovered to a lesser extent. As no, or only a negligible, DNA synthesis took place in the course of seed storage at 30% water content, the recovery from the induced chromosomal aberrations (more exactly the repair of DNA lesions responsible for aberrations) may probably be ascribed to the pre-replication type of repair. No similar recovery was observed after exposure of seeds to X-rays.