Herbicide hormesis to segregate a weed population? – A case study with Tripleurospermum perforatum (Mérat) Lainz

Abstract

Weed populations feature within-population genetic differences. Thus, evaluating mean responses in herbicide treated populations may miss ecologically significant individual responses. Since hormesis can likewise vary between individuals, this study investigated the hypothesis that herbicide hormesis within a high-density weed population is different among slowly-growing individuals, as compared to fast-growing individuals. In a dose-response experiment, Tripleurospermum perforatum (Mérat) Lainz was exposed to 12 doses of Atlantis WG (mesosulfuron + iodosulfuron) in 24 replicates (50 plants/replicate). Root/shoot growth responses were evaluated as dose-response relationships for the population mean, the 90-97th percentile of the population (fast-growing individuals), and the 5-10th percentile (slow-growing individuals). Growth responses were generally biphasic. Slow-growing individuals had more pronounced hormesis that occurred partially at lower doses as compared to the population mean. With fast-growing individuals, hormesis was instead less pronounced and partially shifted to higher doses. Hence, hormesis was primarily associated with a stimulation of slow-growing individuals, while fast-growing individuals contributed to a lesser extent to the hormetic population response in a dense stand in vitro. This discrepancy may have the potential to segregate an herbicide exposed population and alter its sensitivity in the long-run.

Keywords

• biphasic
• dose-response
• growth stimulation
• selective toxicity
• sulfonylurea herbicide