Non-structural carbohydrates (NSC) play an important role in yield formation. In this paper, the relationships of NSC accumulation and translocation with yield formation were investigated under elevated CO2 concentrations ([CO2]) and nitrogen (N) application rates. A japonica rice (Oryza sativa L.) cultivar, “Nanjing 9108,” was grown at three [CO2]—Ambient (T0), ambient + 160 μmol·mol−1 (T1), and ambient + 200 μmol·mol−1 (T2)—in open-top chambers (OTC), with three levels of N fertilizer application rates—10 gN·m−2 (N1), 20 gN·m−2 (N2), and 30 gN·m−2 (N3)—Which were set in OTCs using pot experiments. The results showed that the concentration of NSC (CNSC) and the total mass of NSC stored in stems (TMNSC) under T1 and T2 were higher than those in the T0 treatment, and the CNSC and TMNSC of N3 were lower than those of N1 and N2 at the heading stage. The CNSC and the TMNSC were significantly positively correlated with the stem biomass during the growth period and were notably negatively correlated with the N content in leaves (Nleaf) at the heading and filling stages. The seed setting rate was significantly positively related to the apparent transferred mass of NSC from stems to grains (ATMNSC) at the filling stage, while the relationship between yield and the ATMNSC was not statistically significant. Although there was no difference in the apparent contribution of transferred NSC to grain yield (ACNSC) between treatments, NSC stored in stems further accumulated obviously during the late filling stage, implying that the grain yield of “Nanjing 9108” was predominantly sink-limited. We concluded that elevated [CO2] improved the concentration of NSC at the rice heading stage. The interaction between elevated [CO2] and N fertilizer rates significantly influenced the concentration of NSC at the filling stage. Rice stems NSC reaccumulated at the late grain filling stage, which implies a restriction on NSC transference to grain.

中文翻译：

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CO2浓度升高和施氮水平对粳稻非结构性碳水化合物积累和转移的影响

非结构性碳水化合物 (NSC) 在产量形成中起着重要作用。在本文中，研究了在升高的 CO2 浓度 ([CO2]) 和氮 (N) 施用率下 NSC 积累和易位与产量形成的关系。粳稻 (Oryza sativa L.) 品种“南京 9108”在三个 [CO2] 环境 (T0)、环境 + 160 μmol·mol-1 (T1) 和环境 + 200 μmol·mol-1 下生长(T2)——在开顶室 (OTC) 中，氮肥施用量分为三个级别——10 gN·m-2 (N1)、20 gN·m-2 (N2) 和 30 gN·m-2 ( N3)——使用盆栽实验在 OTC 中设置。结果表明，T1和T2处理的NSC浓度(CNSC)和茎中储存的NSC总质量(TMNSC)高于T0处理，N3处理的CNSC和TMNSC低于N1和N1处理。 N2 在抽穗阶段。CNSC和TMNSC与生育期茎生物量显着正相关，与抽穗期和灌浆期叶片（Nleaf）的N含量显着负相关。结实率与灌浆期NSC表观转移质量(ATMNSC)呈显着正相关，而产量与ATMNSC的关系无统计学意义。尽管不同处理间转移的 NSC 对籽粒产量 (ACNSC) 的表观贡献没有差异，但在灌浆后期储存在茎中的 NSC 进一步积累，这意味着“南京 9108”的籽粒产量主要受汇限制。我们得出结论，升高的 [CO2] 提高了水稻抽穗期 NSC 的浓度。[CO2] 和氮肥施用量之间的相互作用显着影响了灌浆阶段 NSC 的浓度。水稻茎秆 NSC 在灌浆后期重新积累，这意味着 NSC 向籽粒的转移受到限制。