Dataset

Delaying the application of plant growth retardants, such as ethephon, can increase kernel number in maize (<i>Zea mays</i> L.), primarily due to the enhanced assimilate allocation to the ear. However, the underlying physiological and molecular mechanisms remain unclear. To clarify this, we investigated the effects of ethephon application from the 8- to 15-leaf stages (E8–E15) on the physiological mechanisms of kernel development, including changes in internode length, dry matter accumulation and partitioning, and fertilization and kernel set. Additionally, RNA-seq analysis was performed on E14 and the control (water spraying) at the silking stage and 8 days after silking to elucidate the molecular mechanisms underlying the ethephon-mediated kernel number increase. Delaying ethephon application in E14-E15 significantly reduced the internode length below the ear (-26.3% to -23.5%), at the ear internode (-33.9% to -41.2%), and above the ear (-22.9% to -52.5%). The average plant dry matter of E14-E15 increased by 8.1% compared to the control. The ear dry matter of E14 increased by 32.4%, whereas that of E15 remained unchanged. Optimizing the timing of ethephon application in E14-E15 did not negatively affect spikelet number formation but allocated more assimilates to the ear by retarding stem growth, resulting in increased kernel number (+8.3%) and grain yield (+7.4%). In E14, elevated sucrose allocation to the ear at silking resulted in increased T6P accumulation, which subsequently enhanced assimilate import and improved carbohydrate utilization in the post-flowering period. Consequently, at silking, sucrose levels in ears were significantly higher than that in the control, consistent with the enhanced sink capacity. This enhancement was related to the suppression of SnRK1 (sucrose-non-fermenting1-related protein kinase) activity. In contrast, sucrose content was lower post-flowering in E14 due to the up-regulation of T6P-SnRK1 interaction genes at the kernel differentiation stage, which promoted sucrose utilization.