Abstract Although the importance of the critical period for establishing the maize (Zea mays L.) yield components of kernel number (KN) and kernel weight (KW) is well known, there is little detailed information on how early ear development during the critical period and lag phase are influenced by hybrid improvement or N stress. Seven hybrids commercialized between 1946 and 2015 were compared under a range of N stress created by five N fertilizer treatments: no N applied or a total of 220 kg N ha−1 where N was applied either at the four-leaf stage (V4), at flowering, or a combination of these two times. Ears (cobs plus kernels) were sampled five times at weekly intervals, from approximately 14 days before until 14 days after flowering, to determine dry weight, N concentration, and N content. The dynamics of these traits were modeled using an expolinear function and parameters estimated using a non-linear mixed model. Hybrid and N treatment influences on the exponential and linear phases of ear growth were determined by comparing parameters. The greatest impact of genotype or plant N status was realized in the linear phase when modern hybrids exhibited higher linear growth rates and ears accumulated progressively more N with increasing V4 stage N rate. Neither genotype nor N stress resulted in different ear growth or N accumulation rates during the exponential phase; however, modern hybrids exhibited a longer exponential phase duration. Use of expolinear function with parameters estimated within the non-linear mixed models enabled us to gain insight on development phases modified as the result of genetic improvement or affected by N stress. During the exponential phase, which overlaps with the lag phase when cell division is a key determinant of potential kernel weight and sink strength, neither hybrid era nor N treatments substantially impacted ear growth. Instead, the most important early ear growth characteristics to differentially impact final KN and KW at maturity were the duration of the lag phase and ear growth rates during the linear phase. Future research is suggested to unravel how the duration of the exponential phase is related to cell number and kernel size determination, and how these in turn affect kernel growth rate during the linear phase.

中文翻译：

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玉米 (Zea mays L.) 穗生长的指数期和线性期在确定粒数和粒重方面的作用

摘要 虽然关键时期对确定玉米 (Zea mays L.) 籽粒数 (KN) 和籽粒重 (KW) 产量组成部分的重要性众所周知，但关于关键时期早期穗发育的详细信息却很少。和滞后阶段受混合改进或 N 应力的影响。对 1946 年至 2015 年间商业化的七种杂交品种在由五种氮肥处理产生的一系列氮胁迫下进行了比较：不施氮或总共施氮 220 kg N ha-1，其中氮在四叶期 (V4)、在开花时，或这两个时间的组合。从开花前大约 14 天到开花后 14 天，每周对穗（玉米棒加籽粒）进行五次采样，以确定干重、N 浓度和 N 含量。这些性状的动力学使用指数函数建模，参数使用非线性混合模型估计。杂种和氮处理对耳朵生长的指数和线性阶段的影响是通过比较参数来确定的。当现代杂种表现出更高的线性生长速率并且穗随着 V4 阶段 N 速率的增加而逐渐积累更多的 N 时，基因型或植物 N 状态的最大影响在线性阶段实现。在指数期，基因型和氮胁迫都不会导致不同的穗生长或氮积累率。然而，现代混合动力车表现出更长的指数阶段持续时间。使用具有在非线性混合模型中估计的参数的指数函数使我们能够深入了解由于遗传改良或受氮胁迫影响而修改的发育阶段。在指数阶段，当细胞分裂是潜在核重和库强度的关键决定因素时，与滞后阶段重叠，杂交时代和 N 处理都没有显着影响穗生长。相反，对成熟时最终 KN 和 KW 产生不同影响的最重要的早期穗生长特征是滞后期的持续时间和线性阶段的穗生长速率。建议未来研究解开指数阶段的持续时间如何与细胞数量和内核大小确定相关，以及这些反过来如何影响线性阶段的内核生长速率。在指数阶段，当细胞分裂是潜在核重和库强度的关键决定因素时，与滞后阶段重叠，杂交时代和 N 处理都没有显着影响穗生长。相反，对成熟时最终 KN 和 KW 产生不同影响的最重要的早期穗生长特征是滞后期的持续时间和线性阶段的穗生长速率。建议未来研究解开指数阶段的持续时间如何与细胞数量和内核大小确定相关，以及这些反过来如何影响线性阶段的内核生长速率。在指数阶段，当细胞分裂是潜在核重和库强度的关键决定因素时，与滞后阶段重叠，杂交时代和 N 处理都没有显着影响穗生长。相反，对成熟时最终 KN 和 KW 产生不同影响的最重要的早期穗生长特征是滞后期的持续时间和线性阶段的穗生长速率。建议未来的研究解开指数阶段的持续时间如何与细胞数量和内核大小确定相关，以及这些反过来如何影响线性阶段的内核增长率。对成熟时最终 KN 和 KW 产生不同影响的最重要的早期穗生长特征是滞后期的持续时间和线性阶段的穗生长速率。建议未来研究解开指数阶段的持续时间如何与细胞数量和内核大小确定相关，以及这些反过来如何影响线性阶段的内核生长速率。对成熟时最终 KN 和 KW 产生不同影响的最重要的早期穗生长特征是滞后期的持续时间和线性阶段的穗生长速率。建议未来研究解开指数阶段的持续时间如何与细胞数量和内核大小确定相关，以及这些反过来如何影响线性阶段的内核生长速率。