title: Methyl mercury toxicity in plant cultures: modification of resistance and demethylation by light and/or 2,4-dichlorophenoxyacetic acid.
abstract: Cultures of Daucus carota, Ca-68-10, and Lactuca sativa, Le-67, were grown at increasing methyl mercury (MeHg) concentrations ranging from initial doses of 0.05 to 5.0 micrograms/ml per day for 4 days with or without 0.15 microgram/ml 2,4-dichlorophenoxyacetic acid (2,4-D) in the presence or absence of light. The presence of 2,4-D interacted with light synergistically in the expression of MeHg toxicity within the whole range of concentrations. Demethylation patterns increased or decreased depending on the species, the 2,4-D concentration in the medium, and methyl mercury concentration used in the treatment. Lettuce was more sensitive to this interaction than carrot. In lettuce, the presence of 2,4-D in the light lowered the concentration of total Hg (or MeHg) required to reduce growth by 50%, about 13 times relative to that in the dark (i.e., it sensitized the cells). In the absence of 2,4-D the pattern was reversed. In carrot the pattern was similar but less pronounced. This suggests that, in these cell populations, MeHg toxicity is partly a hormone-mediated and light-sensitive event.
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000633:toxicity*; D002734:Chlorophyll / Q000378:metabolism; D003640:Dealkylation; D008027:Light; D008628:Mercury / Q000378:metabolism; D008767:Methylmercury Compounds / Q000528:radiation effects / Q000633:toxicity*; D010944:Plants
chemical_list: D008767:Methylmercury Compounds; D002734:Chlorophyll; D015084:2,4-Dichlorophenoxyacetic Acid; D008628:Mercury