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Title: THE OCCURRENCE OF HORMESIS IN PLANTS AND ALGAE

Author
item CEDERGREEN, NINA - ROYAL VET&AG UNIV-DENMARK
item STREIBIG, JENS - ROYAL VET&AG UNIV-DENMARK
item KUDSK, PER - DANISH INST. OF AG. SCI.
item MATHIASSEN, SOLVEJG - DANISH INST. OF AG. SCI.
item Duke, Stephen

Submitted to: Dose Response
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2007
Publication Date: 5/1/2007
Citation: Cedergreen, N., Streibig, J.C., Kudsk, P., Mathiassen, S.K., Duke, S.O. 2007. The occurrence of hormesis in plants and algae. Dose Response. V. 5:150-162.

Interpretive Summary: Hormesis is the stimulatory effect of a sub toxic dose of a dose. Hormesis with pesticides in target organisms can have environmental toxicology implications. In this work, the occurrence of the phenomenon with herbicides was explored using nine herbicide and a fungicide alone and in combinations with duckweed, an alga, and two terrestrial plants. Hormesis was commonly found with the two herbicides glyphosate and metsulfuron-methyl.

Technical Abstract: This paper evaluated the frequency, magnitude and dose/concentration range of hormesis in four species: The aquatic plant Lemna minor, the micro-algae Pseudokirchneriella subcapitata and the two terrestrial plants Tripleurospermum inodorum and Stellaria media exposed to nine herbicides and one fungicide and binary mixtures thereof. In total, 687 dose-response curves were included in the database. The study showed that both the frequency and the magnitude of the hormetic response depended on the endpoint being measured. Dry weight at harvest showed a higher frequency and a larger hormetic response compared to relative growth rates. Evaluating hormesis for relative growth rates for all species showed that 25% to 76% of the curves for each species had treatments above 105% of the control. Fitting the data with a dose-response model including a parameter for hormesis showed that the average growth increase ranged from 9±1% to 16±16% of the control growth rate, while if measured on a dry weight ases the response increase was 38±13% and 43±23% for the two terrestrial species. Hormesis was found in >70% of the curves with the herbicides glyphosate and metsulfuron-methyl, and in >50% of the curves for acifluorfen and terbuthylazine. The concentration ranges of the hormetic part of the dose-response curves corresponded well with literature values.