Residual mercury in seed of barley (Hordeum vulgare L.) confers genotoxic adaptation to ethyl methanesulfonate, maleic hydrazide, methyl mercuric chloride and mercury-contaminated soil.

Seeds of barley, Hordeum vulgare L., with or without residual mercury were exposed to concentrations of ethyl methanesulfonate (EMS), maleic hydrazide (MH), methyl mercuric chloride (MMCl) and mercury-contaminated soil. Subsequently the endpoints measured were germination, seedling height, mitotic index, mitotic chromosome or spindle aberrations in embryonic shoot cells and meiotic chromosome aberration in pollen mother cells. The results unequivocally demonstrated that the seed-residual mercury conferred protection against the genotoxicity of EMS, MH, MMCl as well as mercury-contaminated soil in barley. The genotoxic adaptation to MH and MMCl was significantly prevented by pre-exposing the Hg-seeds to buthionine sulfoximine, an inhibitor of phytochelatin synthesis. Furthermore, compared to normal seedlings, the seedlings grown from Hg-seeds exhibited a higher amount of non-protein SH. The findings indicated a possible involvement of phytochelatins in the mercury-induced adaptive response.