籽粒氮素获取能力对提高小麦产量和品质非常重要。选用小麦品种豫麦47(高籽粒蛋白含量，15.5%)和豫麦50(籽粒蛋白含量12.4%)，研究了不同施氮水平下小麦植株不同器官营养性N素（AN）、功能性N素（FN）和结构性N素（SN）的变化及其基因型差异。结果表明，花后籽粒从营养器官获取氮素的能力以及利用营养器官氮素形成产量的能力，高蛋白品种豫麦47均显著高于低蛋白品种豫麦50。施氮水平对3类N素含量的影响小于品种效应，且3类N素的品种间差异在花后显著大于花前。在叶片和茎秆中，豫麦50的AN含量从拔节至灌浆期持续下降，而豫麦47持续升高；籽粒中，豫麦50的AN含量花后表现下降（由1.98~2.35 mg g–1下降到1.38~1.70 mg g–1），而豫麦47先降（由5.51~5.70 mg g–1陡降至花后17 d时的1.15~1.38 mg g–1）后升（由1.15~1.38 mg g–1缓慢上升至成熟时的1.29~3.29 mg g–1）。FN含量，两品种间在叶片和茎秆中的差异不显著。SN含量，在叶片和茎秆中两品种不同生育阶段变化趋势基本相同，均先升后降，以开花期最高，但豫麦47比豫麦50花后表现大幅度的显著下降；在籽粒中，两品种均呈现一定的下降趋势。但豫麦47开花时SN含量（3.70%~4.28%）极显著高于豫麦50（1.38%~1.74%），因此，其花后下降幅度也极显著大于豫麦50，3个施氮水平下成熟期比开花期豫麦47分别下降49%、49%和49%，而豫麦50仅下降7%、23%和21%。说明豫麦47籽粒比豫麦50具有较强的从营养器官获取氮素的能力，其开花时籽粒具有较高的SN含量，胚及胚乳细胞分裂对AN的需求较大，为籽粒从营养器官获取较多氮素提供了较大的“源动力”。SN合成决定着氮素的流动方向，是驱使氮素流动的重要因素；叶片和茎秆SN的分解物是花后转运氮素的主要来源。
Wheat grains obtain nitrogen continuously through decomposition and assimilation of nitrogen compounds from vegetative organs after anthesis. The ability of grains obtaining nitrogen is an important factor to improve the yield and quality of wheat. To assess the ability differences, the field experiments were conducted under different nitrogen application rates using two wheat cultivars, Yumai 47 (grain protein content 15.5%) and Yumai 50 (grain protein content 12.4%). The results showed that Grain of Yumai47 had greater ability of obtaining nitrogen from its vegetative organs than that of Yumai 50. To reveal the physiological mechanism causing the difference between the two cultivars, investigation was carried out for the dynamic changes of three nitrogen forms as assimilable nitrogen (AN), functional nitrogen (FN) and structural nitrogen (SN) in wheat plants in responses to varied nitrogen rates. The data showed that AN, FN, and SN were affected more significantly by cultivars than by nitrogen rates, especially after anthesis. AN content in stems and leaves of low grain protein genotype Yumai 50 declined continuously after anthesis, while that of high grain protein genotype Yumai 47 increased. In grains, AN content in Yumai 50 decreased slowly from 1.98–2.35 mg g–1 to 1.38–1.70 mg g–1 after flowering. However, in Yumai 47 it declined sharply from 5.51–5.70 mg g–1 to 1.15–1.38 mg g–1 at 17 days after anthesis, and then increased from 1.15–1.38 mg g–1 to 3.01–3.29 mg g–1 under different nitrogen rates at maturity. The continuous increase of AN content in the stems and leaves from jointing to filling was closely related to the demand of grain protein formation in high protein genotype Yumai 47. FN content, which participated in absorption and assimilation within leaves, was not significantly different in two different genotypes. In addition to a sharper decrease of SN content in Yumai 47 than Yumai 50 after anthesis, SN content in stems and leaves showed a similar trend over development stages. They all increased with a peak at anthesis, and then exhibited a decreasing trend. In grains, changes of SN contents in two cultivars showed a similar trend, decreasing from anthesis to maturity, although Yumai 47 had a much higher SN content (3.70%–4.28%) at anthesis than Yumai 50(1.38%–1.74%). The results suggest that the higher SN content in grains at anthesis is the key factor caused greater nitrogen gain from the vegetative organs in Yumai 47. SN synthesis determines the direction of nitrogen flow, and the decomposition of SN in leaves and stems provided the key source for nitrogen translocation into grain.
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