Abstract Storage of non-structural carbohydrates (NSC) in internode parenchyma before anthesis functions as a major carbon source for rice grain filling. In this study, two-year field and pot experiments with three japonica cultivars and two nitrogen (N) fertilization modes were performed, and dynamics of dry matter (DM) in internodes were quantified from 21 day before anthesis (DBA) to 60 day after anthesis (DAA; maturity). Results showed that in comparison to leaves and sheaths, DM in internodes varied dramatically, with a clear pattern of increasing at 21 DBA, peaking at 10 DAA, then dramatically dropping until 20 or 30 DAA, and finally refilling at maturity. The sharp reduction of dry matter in the internodes corresponded with the fastest rate of grain filling, indicating the importance of internode reserves for yield formation. On the other hand, the high rate of refilling in internodes at late stage implies the excess production of leaf photosynthetic assimilates. Similarly, starch content in internodes showed a pattern of decreasing at 20–30 DAA. To clarify the indicative meaning of internode reserves, we calculated their remobilization rate at 20 DAA and refilling rate at 60 DAA. Genotypic variations existed for the three cultivars, with a range of 15.17 %–36.37 % for remobilization rate and 54.36 %–104.33 % for refilling rates in 2018. Overall, N topdressing significantly increased the translocation of internode reserves for all three cultivars. Furthermore, our calculation showed that only about 10 % of the grain yield was formed during the second month of rice grain filling, indicating this period is less important for grain yield. Our findings help to clarify the significance of internode DM dynamics for rice management and should be beneficial to enhance our knowledge of source and sink relations, the fundamental component of crop yield formation.

中文翻译：

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粳稻灌浆期节间干物质积累动态显示源汇关系

摘要 开花前节间薄壁组织中非结构性碳水化合物 (NSC) 的储存是水稻灌浆的主要碳源。在这项研究中，对三个粳稻品种和两种氮 (N) 施肥模式进行了为期两年的田间和盆栽试验，并量化了从开花前 21 天 (DBA) 到开花后 60 天节间干物质 (DM) 的动态。花期（DAA；成熟期）。结果表明，与叶和鞘相比，节间的 DM 变化显着，在 21 DBA 时增加，在 10 DAA 时达到峰值，然后急剧下降，直到 20 或 30 DAA，最后在成熟时重新填充。节间干物质的急剧减少与最快的籽粒灌浆速度相对应，表明节间储备对产量形成的重要性。另一方面，后期节间的高回填率意味着叶片光合同化物的过量产生。同样，节间淀粉含量在 20-30 DAA 时呈下降趋势。为了阐明节间储备的指示意义，我们计算了它们在 20 DAA 时的再动员率和在 60 DAA 时的再填充率。3 个品种存在基因型变异，2018 年再动员率范围为 15.17%–36.37%，再充填率范围为 54.36%–104.33%。总体而言，施氮显着增加了所有三个品种的节间储量的易位。此外，我们的计算表明，只有大约 10% 的粮食产量是在水稻灌浆的第二个月形成的，这表明这一时期对粮食产量不太重要。