The severity of drought is increasing owing to global climate change. Knowledge about the influence of drought on weeds and herbicide performance is necessary for optimising herbicide applications. Therefore, dose-response trials were conducted to investigate the influence of drought stress on the efficacy of four herbicides. Drought-stressed and non-stressed Hordeum spontaneum seedlings were exposed to nine doses of sulfosulfuron and sulfosulfuron + metsulfuron-methyl. Clodinafop-propargyl and mesosulfuron-methyl + iodosulfuron-methyl sodium were applied to drought-stressed and non-stressed seedlings of Avena sterilis subsp. ludoviciana. Leaf greenness index (SPAD), total chlorophyll content, stomatal conductance and photosynthesis rate of both species were measured. The efficacy of herbicides on H. spontaneum was not influenced by drought stress. In contrast, the performance of herbicides on A. sterilis subsp. ludoviciana was reduced under drought stress, where the ED₅₀ increased by 1.5-fold. The low doses (<2.2 g a.i. ha^−1) of mesosulfuron-methyl + iodosulfuron-methyl-sodium caused hormesis on A. sterilis subsp. ludoviciana. Total chlorophyll content and SPAD index of both species increased due to drought stress. The stomatal conductance and photosynthesis rate of A. sterilis subsp. ludoviciana decreased under drought stress, while H. spontaneum was not influenced. The lack of detrimental effect of drought stress on sulfosulfuron and sulfosulfuron + metsulfuron-methyl performance might be attributed to similar stomatal conductance and photosynthesis rate of the drought-stressed and non-stressed H. spontaneum. The performance reduction in herbicides on drought-stressed A. sterilis subsp. ludoviciana might be owing to the reduction in stomatal conductance and photosynthesis rate. Using adjuvants, diverse formulations and early application of herbicides were suggested for future research to hamper the negative effect of drought on herbicides.

中文翻译：

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干旱胁迫对不育燕麦亚种除草剂性能和光合活性的影响。ludoviciana（冬季野燕麦）和 Hordeum spontaneum（野大麦）

由于全球气候变化，干旱的严重程度正在增加。了解干旱对杂草和除草剂性能的影响是优化除草剂应用所必需的。因此，进行了剂量反应试验以研究干旱胁迫对四种除草剂功效的影响。干旱胁迫和非胁迫大麦幼苗暴露于九个剂量的磺嘧磺隆和磺胺嘧啶 + 甲基磺隆。将炔草酯和甲磺隆+甲基碘磺隆应用于干旱胁迫和非胁迫的Avena sterilis subsp。卢多维西亚纳. 测量了两个物种的叶绿度指数（SPAD）、总叶绿素含量、气孔导度和光合作用速率。除草剂对H . 自发性不受干旱胁迫的影响。相比之下，除草剂对A. sterilis subsp.的性能。ludoviciana在干旱胁迫下减少，其中ED ₅₀增加了 1.5 倍。甲基磺隆 + 甲基碘磺隆的低剂量 (<2.2 g ai ha ^{∼ 1} ) 对A造成兴奋作用。无菌亚种 卢多维西亚纳. 由于干旱胁迫，两个物种的总叶绿素含量和SPAD指数均增加。A. sterilis subsp.的气孔导度和光合作用速率。ludoviciana在干旱胁迫下减少，而H. spontaneum不受影响。干旱胁迫对磺嘧磺隆和磺嘧磺隆+甲基嘧磺隆的性能没有不利影响，可能是由于干旱胁迫和非胁迫H. spontaneum的气孔导度和光合速率相似。除草剂对干旱胁迫的A. sterilis subsp.的性能降低。卢多维西亚纳可能是由于气孔导度和光合作用速率的降低。建议在未来的研究中使用助剂、不同的配方和早期施用除草剂，以阻止干旱对除草剂的负面影响。