Although kernel weight (KW) has proven to be an increasingly important driver behind grain yield (GY) variability in modern maize hybrids, nitrogen’s (N) role in the determination of individual sink capacity (i.e., potential KW) during the lag phase of reproductive development remains unclear. The research objective was to study the relationships between endosperm cell number (ECN) during the lag phase (an indicator of potential KW) and final KW within the context of changing plant N dynamics in field-grown maize during the lag phase. Field experiments tested 3–4 N rates at different plant densities or N timing applications over a 3-year period (2017–2019). Kernels were removed from ears collected at 9, 10, 13, and/or 17 days after silking (DAS) and treated for ECN determination via tissue dissection, staining, enzymatic digestion, and digital microscopy. Plant growth rate, plant N uptake rate, ear growth rate, and ear N allocation rate during the lag phase were studied, as well as plant growth rate during the critical period and its relationship with kernel number per plant. Low N treatments consistently reduced ECN, thereby limiting KW during this early post-silking stage. Following data normalization, the majority of final KW variation was consistently explained by ECN across all experiments and relative DAS sampling times. Nitrogen rate effects on potential KW were not associated with plant growth rate per kernel during the critical period bracketing silking. ECN was highly correlated with ear N allocation rate during the lag phase, but not with plant N uptake rate during that period. Overall, these results show that higher N availability, independently of N timing and plant density, increased final KW by enhancing the sink capacity of individual kernels (at a wide range of kernel numbers per plant) via gains in ECN during lag-period development.

尽管在现代玉米杂交种中，粒重 (KW) 已被证明是谷物产量 (GY) 变异性背后越来越重要的驱动因素，但氮 (N) 在生殖滞后阶段在确定个体汇能力（即潜在 KW）方面的作用发展仍不明朗。研究目标是在滞后期田间玉米植物氮动态变化的背景下，研究滞后期胚乳细胞数 (ECN)（潜在 KW 的指标）与最终 KW 之间的关系。田间试验在 3 年期间（2017-2019 年）测试了不同植物密度或施氮时间下的 3-4 施氮量。从摘丝后 9、10、13 和/或 17 天（DAS）收集的耳朵中取出籽粒，并通过组织解剖、染色、酶消化处理用于 ECN 测定，和数码显微镜。研究了滞后期植株生长速率、植株吸氮率、穗部生长速率和穗部氮分配率，以及关键期植株生长速率及其与单株粒数的关系。低氮处理持续降低 ECN，从而在此早期后丝绸阶段限制了 KW。在数据标准化之后，ECN 在所有实验和相对 DAS 采样时间中一致地解释了大部分最终 KW 变化。施氮量对潜在 KW 的影响与支架抽丝关键时期的每粒植物生长速率无关。ECN 与滞后期的穗氮分配率高度相关，但与该时期的植株氮吸收率无关。总的来说，这些结果表明更高的 N 可用性，