University of Hohenheim, Hans-Ruthenberg Institute, Agroecology Unit, Garbenstraße 13, 70599 Stuttgart, Germany.
University of Hohenheim, Hans-Ruthenberg Institute, Agroecology Unit, Garbenstraße 13, 70599 Stuttgart, Germany; University of Helsinki, Department of Environmental Sciences, Environmental Ecology Unit, Niemenkatu 73, 15140 Lahti, Finland.
Sci Total Environ. 2018 Aug 1;631-632:510-523. doi: 10.1016/j.scitotenv.2018.02.336. Epub 2018 Mar 16.
Toxicants are known to have negligible or stimulatory, i.e. hormetic, effects at low doses below those that decrease the mean response of a plant population. Our earlier observations indicated that at such low toxicant doses the growth of very fast- and slow-growing seedlings is selectively altered, even if the population mean remains constant. Currently, it is not known how common these selective low-dose effects are, whether they are similar among fast- and slow-growing seedlings, and whether they occur concurrently with hormetic effects. We tested the response of Lactuca sativa in complete dose-response experiments to six different toxicants at doses that did not decrease population mean and beyond. The tested toxicants were IAA, parthenin, HHCB, 4-tert-octylphenol, glyphosate, and pelargonic acid. Each experiment consisted of 14,400-16,800 seedlings, 12-14 concentrations, 24 replicates per concentration and 50 germinated seeds per replicate. We analyzed the commonness of selective low-dose effects and explored if toxic effects and hormetic stimulation among fast- and slow-growing individuals occurred at the same concentrations as they occur at the population level. Irrespective of the observed response pattern and toxicant, selective low-dose effects were found. Toxin effects among fast-growing individuals usually started at higher doses compared to the population mean, while the opposite was found among slow-growing individuals. Very low toxin exposures tended to homogenize plant populations due to selective effects, while higher, but still hormetic doses tended to heterogenize plant populations. Although the extent of observed size segregation varied with the specific toxin tested, we conclude that a dose-dependent alteration in size distribution of a plant population may generally apply for many toxin exposures.
有毒物质已知在低于降低植物种群平均反应的剂量下具有可忽略或刺激作用，即 hormetic。我们之前的观察表明，在如此低的有毒物质剂量下，即使种群平均保持不变，快速生长和缓慢生长的幼苗的生长也会被选择性改变。目前，尚不清楚这些选择性低剂量效应有多普遍，它们在快速生长和缓慢生长的幼苗中是否相似，以及它们是否与 hormetic 效应同时发生。我们在不降低种群平均水平的剂量和超出剂量的情况下，用六种不同的有毒物质对 Lactuca sativa 进行了完整的剂量反应实验，测试了其反应。测试的有毒物质是 IAA、蓖麻毒素、HHCB、4-叔辛基苯酚、草甘膦和壬酸。每个实验包括 14400-16800 株幼苗，12-14 个浓度，每个浓度有 24 个重复，每个重复有 50 颗发芽种子。我们分析了选择性低剂量效应的普遍性，并探讨了快速生长和缓慢生长个体之间的有毒效应和 hormetic 刺激是否在与种群水平相同的浓度下发生。无论观察到的反应模式和有毒物质如何，都发现了选择性低剂量效应。与种群平均相比，快速生长个体的毒素效应通常在更高的剂量开始，而缓慢生长个体则相反。由于选择性效应，极低的毒素暴露往往会使植物种群均匀化，而更高但仍 hormetic 的剂量往往会使植物种群多样化。尽管观察到的大小分离程度因具体测试的毒素而异，但我们得出结论，植物种群大小分布的剂量依赖性改变可能普遍适用于许多毒素暴露。
