Liu Lei, Cui Kehui, Qi Xiaoli, Wu Yu, Huang Jianliang, Peng Shaobing
National Key Laboratory of Crop Genetic Improvement, Wuhan, Hubei, China.
Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Wuhan, Hubei, China.
Front Plant Sci. 2023 Aug 3;14:1244281. doi: 10.3389/fpls.2023.1244281. eCollection 2023.
Rice root characteristics are tightly associated with high-efficient nitrogen uptake. To understand the relationship of root plastic responses with nitrogen uptake when reducing nitrogen application for green rice production, a hydroponic experiment and a soil pot experiment were conducted under high (HN) and low (LN) nitrogen applications, using two rice ( L.) varieties, NK57 and YD6, three nitrogen absorption traits (total nitrogen accumulation, net NH influx on root surface, nitrogen uptake apoplasmic pathway) and root characteristics were investigated. In comparison with HN, LN significantly reduced nitrogen absorption and grain yield in both varieties. Concomitantly, there was a decrease in total root length, root surface area, root number, root volume, and root cortical area under LN, while single root length, root aerenchyma area, and root lignin content increased. The expression of and down-regulated in both varieties. The findings revealed that YD6 had smaller reduction degree for the three nitrogen absorption traits and grain yield, accompanied by smaller reduction degree in total root length, root surface area, root cortical area, and expression of the two genes under LN. These root characteristics were significantly and positively correlated with the three nitrogen absorption traits and grain yield, especially under LN. These results indicate that a large root system, lower reduction degree in several root characters, and high expression of genes in YD6 explains its high nitrogen accumulation and grain yield under reduced nitrogen application. The study may provide rationale for developing varieties with low nitrogen fertilizer requirements for enabling green rice production.
水稻根系特征与高效吸氮密切相关。为了解减氮绿色水稻生产中根系可塑性响应与氮吸收的关系，采用水培试验和土培盆栽试验，设置高氮（HN）和低氮（LN）两个水平，以两个水稻品种NK57和YD6为材料，研究了3个氮吸收性状（总氮积累量、根表面净NH₄⁺流入量、质外体途径氮吸收量）及根系特征。与高氮处理相比，低氮处理显著降低了两个品种的氮吸收和籽粒产量。同时，低氮处理下总根长、根表面积、根数量、根体积和根皮层面积均减少，而单根长度、根通气组织面积和根木质素含量增加。两个品种中OsNRT1.1B和OsNAR2.1的表达均下调。结果表明，YD6在3个氮吸收性状和籽粒产量上的降低程度较小，低氮处理下总根长、根表面积、根皮层面积及两个基因的表达降低程度也较小。这些根系特征与3个氮吸收性状和籽粒产量显著正相关，尤其是在低氮处理下。这些结果表明，YD6根系庞大、部分根系性状降低程度较小以及OsNRT1.1B和OsNAR2.1基因高表达，解释了其在减氮条件下的高氮积累量和籽粒产量。该研究可为培育低氮肥需求品种以实现绿色水稻生产提供理论依据。
