Great progress has been achieved in developing hybrid "super rice" varieties in China. Understanding morphological root traits in super rice and the mechanisms of nitrogen acquisition by the root system are of fundamental importance to developing proper fertilisation and nutrient management practices in their production. The present study was designed to study morphological and physiological traits in hybrid super rice roots that are associated with nitrogen use efficiency (NUE). Two hybrid super rice varieties (Yongyou12, YY; Jiayou 6, JY) and one common variety (Xiushui 134, XS) with differing NUE were cultivated hydroponically, and morphological and physiological traits of seedling roots in response to varying nitrogen conditions were investigated. Our results show that the hybrid cultivars YY and JY exhibit larger root systems, arising from a maximisation of root tips and from longer roots without changes in root diameter. The cross-sectional proportion of aerenchyma was significantly higher in super rice roots. The larger root system of super hybrid rice contributed to higher N accumulation and resulted in higher N uptake efficiency. 15N (15NH4+) labeling results show that YY and JY had an enhanced capacity for ammonium (NH4+) uptake. Moreover, YY and JY were more tolerant to high NH4+ and showed reduced futile NH4+ efflux. NH4+ efflux in the root elongation zone, measured by Non-invasive Micro-test Technology, was significantly lower than in XS. Taken together, our results suggest that a longer root, a larger number of tips, a better developed aerenchyma, a higher capacity for N uptake, and reduced NH4+ efflux from roots are associated with higher NUE and growth performance in hybrid super rice.

中文翻译：

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杂交“超级稻”中更高的氮利用效率 (NUE) 与幼苗根部形态和生理性状的改善有关

我国杂交“超级稻”品种开发取得重大进展。了解超级稻的根系形态特征和根系获取氮的机制对于在其生产中制定适当的施肥和养分管理实践至关重要。本研究旨在研究与氮利用效率 (NUE) 相关的杂交超级稻根的形态和生理性状。以不同氮肥效率的2个杂交超级稻品种（永优12、YY；嘉优6、JY）和1个普通品种（秀水134、XS）为研究对象，研究了不同氮素条件下幼苗根系的形态和生理性状。我们的结果表明，杂交品种 YY 和 JY 表现出更大的根系，源于根尖最大化和根部直径没有变化的较长根。超级水稻根系中的横切面组织比例显着较高。超级杂交稻较大的根系有助于更高的氮积累并导致更高的氮吸收效率。15N (15NH4+) 标记结果表明 YY 和 JY 具有增强的铵 (NH4+) 吸收能力。此外，YY 和 JY 对高 NH4+ 的耐受性更高，并显示出无用的 NH4+ 流出减少。通过非侵入性微测试技术测量的根伸长区的 NH4+ 流出量显着低于 XS。综上所述，我们的结果表明，更长的根、更多的尖端、更好的通气组织、更高的 N 吸收能力、