中文摘要：

【目的】比较不同抗倒性超级杂交籼稻抗倒伏性差异及其原因,并分析氮素影响超级杂交籼稻抗倒性的生理机制,以期为水稻高产抗倒伏品种选育与栽培管理提供依据。【方法】以超级杂交籼稻Y两优2号（抗倒伏品种）和Ⅱ优084（易倒伏品种）为材料进行大田试验。2012年设置0、150和300 kg·hm-2 3个氮肥水平,2013年设置135、270和405 kg·hm-2 3个氮水平,比较不同处理倒伏发生率,并从力学、形态学和生理学指标等方面分析倒伏差异的原因。【结果】Y两优2号产量达11.7 t·hm-2,较Ⅱ优084高9.45%。这主要归因于Y两优2号较高的穗粒数及颖花量,二者分别较Ⅱ优084高28.0%和31.8%。与Ⅱ优084比较,Y两优2号成熟期田间倒伏率明显减少,倒伏指数下降19.0%,差异达显著水平,原因是Y两优2号基部节间显著缩短,茎壁明显增厚,叶鞘单位长度干重显著提高,从而弥补了茎秆粗度方面的劣势;其基部节间单位长度茎干重虽略有降低,但结构性碳水化合物含量较高,导致茎秆弯曲应力和折断弯矩显著增加,抗倒伏性提高。随施氮量增加,超级杂交籼稻基部节间茎秆折断弯矩显著降低,导致倒伏指数显著上升。大幅增加氮肥水平显著降低了抽穗期单茎鞘干重和灌浆后期基部节间单位长度叶鞘干重,从而使得茎秆质量变劣,且叶鞘对茎秆的保护和支持能力降低;此外,基部节间茎、鞘中木质素含量明显降低,茎秆弯曲应力和折断弯矩随之下降,倒伏风险增加。Ⅱ优084在较低的施氮水平下,折断弯矩大幅降低,甚至低于Y两优2号高氮水平,导致倒伏指数明显上升,尽管增加氮素用量未能显著增加其倒伏率,却较大幅度地降低了产量。【结论】缩短基部节间长度,增加茎壁厚度以弥补茎秆粗度不足的劣势,增加叶鞘充实程度,提高对茎秆的保护和支撑作用,是增强超级杂交籼稻茎秆机械强度和抗倒伏性的主要途径。

英文摘要：

【Objective】 Experiments were conducted with two super-hybrid rice varieties which have a big difference in lodging resistance. The main objective of this study was to reveal the mechanisms of the divergence of lodging resistance and effects of nitrogen on rice lodging resistance between super-hybrid rice varieties. Results of the study will provide a theoretical basis for breeding and nitrogen management for high yield of rice. 【Method】 Experiments were conducted with super-hybrid rice Yliangyou2 which is strong in lodging resistance and Ⅱyou084 which is weak in lodging resistance to compare their difference in lodging resistance between the two varieties and study the effects of nitrogen on rice morphological, mechanical and physiological traits. In 2012, 0, 150, and 300 kg N·hm-2 were applied. In 2013, 135, 270, and 405 kg N·hm-2 were arranged. 【Result】 The yield of Yliangyou2 reached 11.7 t·hm-2, 9.45% higher than IIyou084. This was mainly attributed to the higher number of spikelets per panicle and spikelets per hectare, which were 28.0% and 31.8% higher than IIyou084, relatively. The lodging index of Yliangyou2 reduced significantly at mature stage, 19.0% higher than IIyou084. This was because the disadvantage of the culm diameter of Yliangyou2 was compensated by the decreased length of the basal internode, thickened stem wall and significant increased dry weight per unit length of leaf sheath. For Yliangyou2, although there was no significant advantage in dry weight per unit length of culm, high structural carbohydrate content lead to the significant increasing of the lodging resistance. With the nitrogen increasing, the lodging index of the super-hybrid indica rice increased significantly as the reduction of the bending moment at breaking. The quality of the stem at heading stage was deteriorated with the excessive nitrogen fertilizer, as a result, the mechanical strength of stem dropped with the dry weight per unit length of basal leaf sheath. In addition, the lignin content of basal stem