Interactive patterns of methyl mercury toxicity in nuclear and cell division of apical meristems of Elodea densa at low concentrations and long-term exposures in vivo

Abstract

CZUBA, M., and D. C. MORTIMER. 1982. Interactive patterns of methyl mercury toxicity in nuclear and cell division of apical meristems of Elodea densa at low concentrations and long-term exposures in vivo. Can. J. Bot. 60: 657-666. Elodea densa plants continuously exposed to low levels of methylmercury (7.5 X lo-'' to 7.5 X lo-' M) in a flowing water system over a 25-day period concentrated methylmercury in young tissues. Toxicity effects in apical meristems were not linear with dose and time but were interactive in response. Microscopic studies of plants treated at 7.5 X 10-'OM showed a predominance of "spaghetti" prophases, a gradual inhibition of mitosis, and imbalance of mitotic stages. Higher concentrations of methylmercury produced different effects: bi-and multi-nucleate cells, polyploidy , aneuploidy , and altered or incomplete cell walls. At the highest concentrations (7.5 X 10-'M) total pycnosis developed in the apex within 11 days, followed by a disintegration of nuclear and cell contents. Demethylation in tissues was directly related to methylmercury concentrations in the tissues and to tissue age.

Mercury uptake and enzymatic response of Posidonia oceanica after an experimental exposure to organic and inorganic forms

“…Few data concerning natural methylmercury concentrations in aquatic plants are available in the literature. The proportions 85.8% methylmercury and 13.9% mercury chloride were reported [31] in the tips of the plant E. densa. In the present study, the inorganic form seemed to be predominantly lost when sheaths presented lower mercury contents than controls.…”