Drought is one of the most detrimental crop stresses that substantially impede maize productivity globally. This study subjected maize plants at the vegetative/generative transition phase to three soil water treatments (WW, well-watered, soil moisture at 80 ± 5%; WD1, water-deficit 1, soil moisture at 60 ± 5%; WD2, water-deficit 2, soil moisture at 45 ± 5%) to investigate the effect of drought on young ear development. Subsequently, the differentiation and size of ears were evaluated, along with carbohydrates quantification and RNA-sequencing of the ear. The maize leaf photosynthesis and plant growth parameters were also measured. The results showed that WD1 and WD2 decreased the total biomass by 54.3 % and 61.4 % at 54 days after emergence (DAE). Compared to other plant organs, the ear and leaf contributed the most to the biomass decrease. The diameter of ears under WD1 and WD2 were significantly decreased by 30.0 % and 50.0 %, respectively, at 54 DAE. Interestingly, transcriptome analysis of the ears at 54 DAE indicated that the differentially expressed genes in WD2 mainly participated in starch and sucrose metabolism. Furthermore, the starch, glucose, and sucrose contents of WD2 were significantly reduced. Notably, WD2 significantly decreased the leaf photosynthetic capacity. Meanwhile, WD1 and WD2 significantly reduced the net assimilation rate and enhanced the specific leaf weight at 44 DAE. However, no change was found at 54 DAE. Finally, WD1 and WD2 decreased the length and diameter of the ear at harvest, especially the export proportion and conversion proportion of leaves during the grain filling stage. In summary, soil WD decreases assimilate accumulation in maize plants and metabolism in young ears, hence suppressing ear development during the vegetative/generative transition phase.

干旱是严重阻碍全球玉米生产力的最有害的作物压力之一。本研究对处于营养/生成过渡阶段的玉米植物进行了三种土壤水分处理（WW，充足浇水，土壤水分为 80±5%；WD1，缺水 1，土壤水分为 60±5%；WD2，水- 缺陷 2，土壤湿度为 45 ± 5%）以研究干旱对幼穗发育的影响。随后，评估了耳朵的分化和大小，以及耳朵的碳水化合物定量和 RNA 测序。还测量了玉米叶片光合作用和植物生长参数。结果表明，WD1和WD2在出苗后54天（DAE）使总生物量减少了54.3%和61.4%。与其他植物器官相比，穗和叶对生物量减少的贡献最大。WD1 和 WD2 下的耳朵直径在 54 DAE 时分别显着降低了 30.0% 和 50.0%。有趣的是，在 54 DAE 时对耳朵的转录组分析表明，WD2 中差异表达的基因主要参与淀粉和蔗糖代谢。此外，WD2 的淀粉、葡萄糖和蔗糖含量显着降低。值得注意的是，WD2 显着降低了叶片的光合能力。同时，WD1和WD2在44 DAE时显着降低了净同化率并提高了比叶重。但是，在 54 DAE 没有发现任何变化。最后，WD1和WD2降低了收获时穗的长度和直径，特别是灌浆期叶片的输出比例和转化比例。总之，