Herbicides have been shown to reduce flower production and to delay flowering, with results varying among herbicides and tested plant species. We investigated the effects of herbicides on flowering in an extensive greenhouse study conducted in Canada and Denmark. The effects of low doses of 5 different herbicides (bromoxynil, ioxynil + bromoxynil, metsulfuron-methyl, clopyralid, and glyphosate), simulating realistic drift scenarios (1 and 5% recommended field rates), on plant flowering were examined using 9 wild plant species exposed at either the seedling (6- to 8-leaf) or flower bud stage. Following herbicide exposure, initial flowering date as well as flower production over time were recorded over the growing period. The effect of herbicides on cumulative flower numbers and flowering time were modeled using Gompertz growth models. Significant delays to peak flowering and/or reductions in flower production were observed in at least one plant species for all tested herbicides, with glyphosate often exhibiting the greatest negative effects, that is, plant death. Except for ioxynil + bromoxynil, there was no clear evidence of either the seedling or the flower bud stage being more sensitive. Overall, 58% of all species × life stage × herbicide treatments resulted in either a statistically significant or a strong decline in flower production with herbicide application rates up to 5% of recommended field rates, whereas significant or strong delays in peak flowering were also detected but were slightly less common. Effects at 1% label rates were minimal. Simultaneous delays to peak flowering and reductions in total flower production occurred in approximately 25% of all cases, indicating that herbicide application rates simulating realistic drift scenarios would likely have negative effects on wild floral communities. Environ Toxicol Chem 2020;39:1244-1256. © 2020 SETAC.

中文翻译：

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除草剂对开花的影响。

研究表明，除草剂可减少花的产生并延缓开花，结果在除草剂和受试植物之间有所不同。在加拿大和丹麦进行的广泛温室研究中，我们调查了除草剂对开花的影响。使用9种野生植物物种检验了低剂量的5种不同除草剂（溴苯苄腈，苯乙腈+溴苯腈，甲基磺隆，甲基吡虫啉和草甘膦）对现实漂移情况（1和5％推荐田间速率）的模拟效果。在苗期（6至8片）或花蕾期暴露。暴露于除草剂之后，记录了整个生长期的起始开花日期以及随时间的花产量。使用Gompertz生长模型模拟了除草剂对累积花数和开花时间的影响。对于所有测试的除草剂，在至少一种植物物种中观察到峰值开花的明显延迟和/或花的产量的减少，草甘膦通常表现出最大的负面影响，即植物死亡。除艾诺尼+溴艾诺尼外，没有明确的证据表明苗期或花蕾期更敏感。总体而言，所有物种中的58％×生命周期×除草剂处理导致花卉产量出现统计学上的显着下降或强烈下降，除草剂的施用量高达建议田间施用量的5％，而峰值花期也出现了显着或强烈的延迟但较不常见。标记率为1％的影响极小。在所有案例中，大约有25％同时出现了花期高峰延迟和总花期减少的情况，表明除草剂的施用量模拟了实际的漂流情景，可能会对野生花卉群落产生负面影响。Environ Toxicol Chem 2020; 39：1244-1256。©2020 SETAC。