Damage and recovery from drift of synthetic-auxin herbicide dicamba depends on concentration and varies among floral, vegetative, and lifetime traits in rapid cycling Brassica rapa

Herbicides can drift from intended plants onto non-target species. It remains unclear how drift impacts plant functional traits that are important for fitness. To address this gap, we conducted an experiment where fast cycling Brassica rapa plants were exposed to one of three drift concentrations (0.5%, 1%, 10%) of synthetic-auxin dicamba. We evaluated damage to and capacity of floral and vegetative traits to recover as well as lifetime fitness by comparing treated plants to controls. Response to dicamba exposure was concentration-dependent across all traits but varied with trait type. At 0.5% dicamba, three out of five floral traits were affected, while at 1% dicamba, four floral traits and one out of two vegetative traits were negatively impacted. At 10% dicamba all floral and vegetative traits were stunted. Overall, floral traits were more responsive to all dicamba drift concentrations than vegetative traits and displayed a wide range of variation ranging from no response (e.g., pistil length) to up to 84% reduction (ovule number). However, despite floral traits were more affected across the dicamba drift concentrations they were also more likely to recover than the vegetative traits. There was also variation among lifetime traits; the onset of flowering was delayed, and reproductive fitness was negatively affected in a concentrationdependent manner, but the final biomass and total flower production were not affected. Altogether, we show substantial variation across plant traits in their response to dicamba and conclude that accounting for this variation is essential to understand the full impact of herbicide drift on plants and the ecological interactions these traits mediate.

除草剂可从靶标植物漂移至非靶标物种。目前尚不清楚此类漂移如何影响对植物适合度至关重要的植物功能性状。
为填补这一研究空白，本研究开展了一项实验：将快速循环型芸薹（Brassica rapa）暴露于三种模拟漂移浓度的人工合成生长素类除草剂麦草畏（dicamba）溶液（0.5%、1%、10%）中。通过比较处理组与对照组植株，本研究评估了花器官与营养器官性状的受损程度、恢复能力，以及植株终生适合度。
所有性状对麦草畏暴露的响应均呈浓度依赖性，但因性状类型不同而存在差异。当麦草畏浓度为0.5%时，5个花器官性状中有3个受到影响；浓度为1%时，4个花器官性状与2个营养器官性状中的1个受到显著负面影响；当浓度达10%时，所有花器官与营养器官性状均出现发育受阻。
总体而言，相较于营养器官性状，花器官性状对所有麦草畏漂移浓度的响应更为敏感，其变异幅度跨度极大：从无响应（如花柱长度）到最高达84%的降幅（如胚珠数量）。尽管花器官性状在各麦草畏漂移浓度下受影响程度更高，但它们相较于营养器官性状也更易恢复。
终生相关性状间也存在差异：开花起始时间延后，生殖适合度以浓度依赖的方式受到负面影响，但植株最终生物量与总花量未受影响。
综上，本研究证实植物不同性状对麦草畏的响应存在显著差异，并得出结论：只有纳入这一变异维度，才能全面理解除草剂漂移对植物及其性状所介导的生态相互作用的完整影响。