Table1.DOCX

Floret development is critical for grain setting in wheat (Triticum aestivum), but more than 50% of grain yield potential (based on the maximum number of floret primordia) is lost during the stem elongation phase (SEP, from the terminal spikelet stage to anthesis). Dynamic plant (e.g., leaf area, plant height) and floret (e.g., anther and ovary size) growth and its connection with grain yield traits (e.g., grain number and width) are not clearly understood. In this study, for the first time, we dissected the SEP into seven stages to investigate plant (first experiment) and floret (second experiment) growth in greenhouse- and field-grown wheat. In the first experiment, the values of various plant growth trait indices at different stages were generally consistent between field and greenhouse and were independent of the environment. However, at specific stages, some traits significantly differed between the two environments. In the second experiment, phenotypic and genotypic similarity analysis revealed that grain number and size corresponded closely to ovary size at anthesis, suggesting that ovary size is strongly associated with grain number and size. Moreover, principal component analysis (PCA) showed that the top six principal components PCs explained 99.13, 98.61, 98.41, 98.35, and 97.93% of the total phenotypic variation at the green anther, yellow anther, tipping, heading, and anthesis stages, respectively. The cumulative variance explained by the first PC decreased with floret growth, with the highest value detected at the green anther stage (88.8%) and the lowest at the anthesis (50.09%). Finally, ovary size at anthesis was greater in wheat accessions with early release years than in accessions with late release years, and anther/ovary size shared closer connections with grain number/size traits at the late vs. early stages of floral development. Our findings shed light on the dynamic changes in plant and floret growth-related traits in wheat and the effects of the environment on these traits.

小花发育对普通小麦（Triticum aestivum）的结实至关重要，但基于小花原基最大数量计算的籽粒产量潜力中，有超过50%在茎伸长阶段（SEP，从顶端小穗期至开花期）流失。植株（如叶面积、株高）与小花（如花药、子房大小）的动态生长过程，及其与籽粒产量性状（如籽粒数、粒宽）的关联机制，目前尚未完全阐明。本研究首次将茎伸长阶段划分为7个时期，分别针对大田与温室种植的小麦开展植株生长（试验一）与小花生长（试验二）相关研究。试验一结果显示，不同时期的多项植株生长性状指标在大田与温室环境下总体保持一致，且不受环境影响；但在特定时期，部分性状在两种环境间存在显著差异。试验二中，表型与基因型相似性分析表明，开花期的籽粒数与籽粒大小与子房大小高度相关，提示子房大小与籽粒数、籽粒大小存在紧密关联。此外，主成分分析（principal component analysis, PCA）结果显示，前6个主成分（PCs）分别在绿花药期、黄花药期、挑旗期、抽穗期及开花期，可解释总表型变异的99.13%、98.61%、98.41%、98.35%及97.93%。第一主成分所解释的累积方差随小花发育进程逐渐降低：绿花药期达到最高值（88.8%），开花期则降至最低（50.09%）。最后，开花期的子房大小在早审定年份的小麦种质中显著大于晚审定年份的种质；且花药/子房大小与籽粒数/籽粒大小性状的关联强度，在小花发育后期较前期更为紧密。本研究结果阐明了小麦植株与小花生长相关性状的动态变化规律，以及环境对这些性状的调控作用。