Absence of DNA repair replication after chemical mutagen damage in Vicia faba

Exposure of human (Hela) cells to the mutagens 4-nitroquinoline-1-oxide (4NQO) and N-methyl-N′-nitro-nitrosoguanidine (MNNG) produces damage in DNA that is repaired by a mechanism involving the insertion of new bases into DNA (repair replication). Vicia faba root tips, either from soaked seeds containing non-proliferating cells or from growing roots, do not perform detectable amounts of repair replication even though the mutagens inhibit DNA synthesis and cause chromosome aberrations. In view of similar failures to resolve excision in Chlamydomonas, Haplopappus, and Nicotiana after irradiation with UV light and in Vicia faba after X-irradiation it appears that plants in general might lack this repair process.