The ovary-to-grain transition process is crucial for individual grain weight potential, but the but the physiological regulation of this highly dynamic and complex developmental process remains largely unknown unknown. Here, we performed a high temporal-resolution analysis of the proximal (large) and distal (small) ovaries/grains collected at an interval of 3 days from the booting stage to maturity stage. During grain-filling process, proximal grains always maintained a greater dry matter (0–36 days after anthesis, DAA), water (0–33 DAA), sugar (3–33 DAA), protein (6–36 DAA), and starch (amylose and amylopectin, 18–36 DAA) content, and larger volume (-15–36 DAA) than distal grains, but their partition or concentration did not differ between the proximal and distal grains. This result suggested that the capability of proximal and distal grains to produce water, sugar, protein, and starch within the same volume was similar; thus, grain sink (i.e. volume) was the cause in determinant of grain weight potential. In fact, the proximal ovary had a larger volume and related parameters (length, width and thickness) than the distal ovary before anthesis stage. in addition, the correlation coefficients of length and width with volume are higher than the correlation coefficients of thickness with volume. Clearly, we discovered a dynamic physiological mechanism for high proximal grain weight: the rapid elongation and widening of the proximal ovary improved its size, which passed to the proximal grain a volume advantage in the following ovary-grain transition, which allowed it to took up more sucrose and then converted into more starch and protein, improving dry matter accumulation and increasing proximal grain weight. Our findings provide a precise strategy for breeding and cultivation to increase individual grain weight potential by improving ovary volume.

中文翻译：

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子房形态决定子房到籽粒的转变过程和小麦的最终粒重潜力


子房到籽粒的转变过程对于个体籽粒重量潜力至关重要，但这种高度动态和复杂的发育过程的生理调节仍然很大程度上未知。在这里，我们对从孕穗阶段到成熟阶段每隔 3 天收集的近端（大）和远端（小）子房/籽粒进行了高时间分辨率分析。在灌浆过程中，近端籽粒始终保持较高的干物质（花后0-36天DAA）、水（0-33 DAA）、糖（3-33 DAA）、蛋白质（6-36 DAA）和淀粉（直链淀粉和支链淀粉，18-36 DAA）含量和体积（-15-36 DAA）比远端谷物大，但它们的分配或浓度在近端和远端谷物之间没有差异。这一结果表明，近端和远端谷物在相同体积内产生水、糖、蛋白质和淀粉的能力相似；因此，谷物下沉（即体积）是决定谷物重量潜力的原因。事实上，在开花期之前，近端卵巢的体积和相关参数（长度、宽度和厚度）比远端卵巢更大。另外，长度和宽度与体积的相关系数高于厚度与体积的相关系数。显然，我们发现了高近端粒重的动态生理机制：近端子房的快速伸长和加宽改善了其尺寸，这在随后的子房-粒重转变中将体积优势传递给近端粒，使其能够占据更多的蔗糖，然后转化为更多的淀粉和蛋白质，改善干物质积累并增加近粒重。 我们的研究结果为育种和栽培提供了精确的策略，通过改善子房体积来增加个体粒重潜力。