氮肥后移对不同氮效率水稻花后碳氮代谢的影响

摘要

The optimal nitrogen (N) managements and the selection of genotypes with high N use efficiency (NUE) play a vital role in rice production aiminged at high yield and high NUE. Two rice cultivars, one with high-NUE (Dexiang 4103) and the other with low-NUE (Yixiang 3724) were used in pot and field experiments in 2013 and 2014. The total N fertilizer applied was 180 kg ha?1 of urea and three treatments were included: 1) 50% basal dressing, 30% topdressing at 7 d after transplanting (DAT), and 20% topdressing at 4th leaves emerged from the top (N1), 2) 30% basal dressing, 30% topdressing at 7 DAT, 40% topdressing was split into two equal applications at 4th and 2nd leaves emerged from the top, 3) 20% basal dressing, 20% topdressing at 7 DAT, 60% topdressing was split into two equal applications at 4th and 2nd leaves emerged from the top, respectively. Double isotope tracing technique of13C and15N and physiological-biochemical analysis were used to study the accumulation, translocation, dis-tribution of N and photosynthate, and the correlation between morphology and physiological-biochemical characteristics and their relationships with grain yield. There were significant effects of cultivars and N application modes on grain yield, as well as the absorption and translocation of N and photosynthate from full-heading to maturity stage. Compared with N1and N3, N2 treatment with high-NUE was the best model in this paper referred as the variety and N application coupling model, which could improve N accumulation in rice plant after anthesis, increase photosynthetic rate, activities of ribulose 1,5-bisphosphate carboxylase, and glutamine synthetase in flag leaves, promote accumulation and translocation of photosynthate and N, and then improve the yield and NUE. Double isotope labeling results showed that the accumulation amount of photosynthetic products and N in rice plant with high-NUE was 7.78–12.75 mg13C plant–1 and 15.14–18.78 mg15N plant–1 higher, the translocation amount of photosynthate and N in leaves with high-NUE was 1.70–2.93 mg13C plant–1, 2.21–4.55 mg15N plant–1 higher, the translocation amount of pho-tosynthate and N in leaf sheaths with high-NUE was 1.70–2.93 mg13C plant–1, 0.05–1.14 mg15N plant–1 higher than those with low-NUE, respectively. From full-heading to maturity stage,13C photosynthate in the spike with high-NUE and low-NUE respec-tively increased by 31.04–44.68 mg13C plant–1(accounting for 42.04%–46.38% of total amount of13C) and 24.94–34.26 mg13C plant–1 (accounting for 36.45%–41.36% of total amount of13C), while,15N accumulation in the spike with high-NUE and low-NUE respectively increased by 35.56–46.58 mg15N plant–1(accounting for 61.82%–82.93% of total amount of15N) and 27.37–31.57 mg15N plant–1 (accounting for 58.04%–68.31% of total amount of15N). Compared with low-NUE, the high NUE rice cultivar is more beneficial to the accumulation and translocation of photosynthate, with higher N absorption capacity, stronger N translocation ability, and stronger C and N metabolism capacity in leaves, satisfying the N demand of plants during their grain forming stage, which is the important reason for high-NUE rice cultivar further to increase yield and NUE. From, the information of C/N ratio in different organs after-anthesis, combined with the results of high yield and high NUE in different varieties under N2 treatment, from full-heading to maturity stage, the C/N increasing range in leaf and panicle is the same as the reducing range in leaf sheaths and roots. Therefore, C/N ratio in different organs from full-heading to maturity stage might be a candidate indicator for high yield and high NUE in rice production.%以氮高效品种(德香4103)和氮低效品种(宜香3724)为材料,利用13C和15N双同位素示踪技术和生理生化分析方法,采用盆栽及大田试验,在施氮量180 kg hm–2条件下,设置3种氮肥运筹方式,基肥:蘖肥:穗肥比例分别为5:3:2(N1)、3:3:4(N2)、3:1:6(N3),以及不施氮(N0)处理;研究其对不同氮效率水稻花后氮碳代谢的影响,并探讨氮肥后移下花后光合同化物及氮素累积、转运、分配的共性响应机制及其与产量的关系.结果表明,品种、氮肥运筹对花后氮素利用特征、光合同化物分配、生理特性及产量均存在显著影响.氮高效品种与氮肥后移量占总施氮量的40%、氮素穗肥运筹以倒四、倒二叶龄期等量追施相配套(N2处理),能促进花后氮素累积,提高剑叶光合速率和1,5-二磷酸核酮糖羧化酶、谷氨酰胺合成酶等碳氮代谢关键酶活性,促进叶片、茎鞘、根系、穗各营养器官光合同化物及氮素累积与转运,进而提高产量及氮肥利用率,为本试验氮高效品种配套的氮肥运筹优化模式.花后不同氮肥运筹下,氮高效品种光合同化物、氮素的累积与转运,分别较氮低效品种高7.78~12.75 mg13C株–1、15.14~18.78 mg15N株–1;且叶片转运量分别较氮低效品种高1.70~2.93 mg13C株–1、2.21~4.55 mg15N株–1,茎鞘转运量分别较氮低效品种高1.70~2.93 mg13C株–1、0.05~1.14 mg15N株–1;而穗部氮高效与氮低效品种13C同化物分别增加31.04~44.68 mg13C株–1(占13C总量的42.04%~46.38%)、24.94~34.26 mg13C株–1(占13C总量的36.45%~41.36%),15N则分别增加35.56~46.58 mg15N株–1(占15N总量的61.82%~82.93%)、27.37~31.57 mg15N株–1(占15N总量的58.04%~68.31%).氮高效品种花后具有强光合碳同化、氮素的协同吸收转运特征,以及碳氮代谢能力,来满足籽粒灌浆期对光合同化物及氮素的利用,是氮高效品种相对于氮低效品种高产、氮高效利用的重要原因.此外,从花后不同器官碳氮比(C/N)变化值综合两品种高产及氮肥高效利用来看,N2处理下,齐穗至成熟期叶片、穗部C/N提高幅度与该时期茎鞘、根系C/N降低幅度一致,据此可将C/N作为水稻高产及氮肥高效利用同步提高的评价指标,这具有重要的参考价值.