Plant N nutrition and preharvest stem nonstructural carbohydrates (NSCs) greatly influence ratoon crop yield in a riceratoon-rice system. However, their physiological relationships haven’t been unraveled. We designed this study to test whether greater rice regeneration ability due to preharvest N application is accompanied by increased stem reserves, or whether plant N nutrition and stem reserves independently influence regeneration. First, we evaluated ratooning of crops that receive N after the main crop’s late reproductive stage. Second, we imposed shade to decrease light intensity by 64 %69 % during grain filling of the main crop, and measured the effects of N application on NSCs of the main crop and ratoon crop growths in 2 years. N applied at 5 days after heading of the main crop consistently increased the regeneration ability and ratoon crop yield under non-shaded condition. It did not increase the regeneration ability under heavy shade, when only small amounts of stem NSCs accumulated. Without shade, N application at 5 days after heading increased the concentration of stem NSCs in only one of the two years, whereas the regeneration ability and ratoon crop yield increased in both years. Our results suggest that the increase in ratoon crop yield with preharvest N application requires more than a threshold amount of stem NSCs before the main crop is harvested. However, the preharvest N application can also promote tiller regeneration without further accumulation of stem reserves. N management for ratoon crops therefore depends on light conditions and the main crop’s stem reserves. The relationships between plant N, stem reserves, and regeneration ability revealed here will support improved N management for ratoon rice cultivation.

中文翻译：

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不同茎秆储量下水稻对采前施氮的响应


在稻仓-稻米系统中，植物氮营养和采前茎非结构性碳水化合物 （NSC） 对再生作物产量有很大影响。然而，他们的生理关系还没有被解开。我们设计了这项研究来测试采前施用氮导致水稻再生能力的增强是否伴随着茎储备的增加，或者植物氮营养和茎储备是否独立影响再生。首先，我们评估了在主要作物的晚期繁殖阶段后接受 N 的作物的生长情况。其次，在主作物灌浆过程中加阴降低光照强度 64 %69 %，并测量了 2 年施氮对主作物 NSCs 和再生作物生长的影响。在主要作物抽穗后 5 d 施氮在无阴条件下持续提高再生能力和再生作物产量。在重阴下，当只有少量的茎 NSCs 积累时，它不会增加再生能力。在没有阴凉处，抽穗后 5 d 施氮仅在 2 年中有 1 年增加了茎 NSCs 浓度，而 2 年再生能力和再生作物产量都有所增加。我们的结果表明，在收获主要作物之前，采前施用氮肥可以提高再生作物产量，需要超过阈值量的茎 NSC。然而，采前施氮也可以促进分蘖再生，而不会进一步积累茎储备。因此，再生作物的氮管理取决于光照条件和主要作物的茎储备。这里揭示的植物氮、茎储备和再生能力之间的关系将有助于改进再生稻种植的氮管理。