Context

Cereal nitrogen economy throughout the whole crop cycle is a critical driver of biomass and grain production, but while some periods of N deficiency have a detrimental impact on grain yield, others exert no effect. An appropriate indicator of the N nutritional status of a crop is the N nutrition index (NNI).

Objective

i. to quantify NNI from mid tillering until anthesis; ii. to analyze its effects on the capture and use of radiation and biomass production; iii. to highlight cultivar variability in these traits.

Methods

A three-year field trial was carried out in a Mediterranean climate to assess NNI of four durum wheat (Triticum turgidum ssp. durum Desf.) cultivars grown under three N fertilization rates (0, 80 and 160 kg N ha⁻¹) from mid tillering until anthesis, and analyze its effects on radiation capture (LAI and fraction of intercepted radiation, FIPAR) and use (RUE, Radiation Use Efficiency)

Results

The level of N shortage imposed with the N0 treatment increased from a moderate shortage at tillering (NNI = 0.86 on average) to a maximum N stress at anthesis (NNI = 0.45). The relationship between NNI and RUE was linear until booting, but became curvilinear at anthesis.The relative response of LAI to NNI variation was greater than that observed for RUE, but it did not affect proportionally the FIPAR because the LAI values above 2 observed after tillering already assured an FIPAR between 75% and 92%,. Cultivar Aureo was characterized by the greater NNI (frequently above 1), N uptake, and N allocated to pseudo-stems across all developmental stages.

Conclusion

All the cultivars shared common relationships between NNI and RUE, LAI and FIPAR, implying that differences between cultivars in RUE, LAI and FIPAR were partly due to their different NNIs and not to a different response to NNI. RUE was more sensitive to NNI variation than radiation interception expressed as FIPAR, but using LAI as a proxy for radiation interception gives opposite results.

Implication

Lines with high potential grain protein percentages may be selected early in the season using NNI above 1 as selection criterium. Cultivars, such as Aureo, which are able to store large quantities of N in their vegetative tissues and attain high NNI values at anthesis are penalized in terms of their RUE during the period in which the potential grain number is determined.

中文翻译：

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不同发育阶段硬粒小麦品种氮素状况对辐射捕获和利用的影响

语境

贯穿整个作物周期的谷物氮经济是生物量和粮食生产的关键驱动力，但虽然某些时期缺氮对粮食产量有不利影响，但其他时期则没有影响。作物氮营养状况的一个适当指标是氮营养指数 (NNI)。

客观的

我。量化从分蘖中期到开花期的 NNI；二. 分析其对辐射的捕获和使用以及生物质生产的影响；三. 以突出这些性状的品种变异性。

方法

在地中海气候条件下进行了为期三年的田间试验，以评估在三种施氮率（0、80 和 160 kg N ha ⁻¹）下从中期开始生长的四种硬粒小麦 ( Triticum turgidum ssp. durum Desf.) 品种的 NNI分蘖至开花期，并分析其对辐射捕获（LAI 和截获辐射分数，FIPAR）和使用（RUE，辐射使用效率）的影响

结果

N0 处理造成的氮短缺水平从分蘖时的中度短缺（平均 NNI = 0.86）增加到开花期的最大氮胁迫（NNI = 0.45）。NNI 和 RUE 之间的关系在孕穗前呈线性，但在开花期变为曲线。LAI 对 NNI 变化的相对响应大于观察到的 RUE，但它对 FIPAR 没有成比例的影响，因为在分蘖后观察到 LAI 值大于 2已经保证 FIPAR 在 75% 到 92% 之间。品种 Aureo 的特点是更高的 NNI（通常高于 1）、N 吸收和 N 在所有发育阶段分配给假茎。

结论

所有品种在 NNI 和 RUE、LAI 和 FIPAR 之间都有共同的关系，这意味着 RUE、LAI 和 FIPAR 之间的差异部分是由于它们的 NNI 不同，而不是对 NNI 的不同反应。RUE 比表示为 FIPAR 的辐射拦截对 NNI 变化更敏感，但使用 LAI 作为辐射拦截的代理给出相反的结果。

含义

可以在季节早期使用高于 1 的 NNI 作为选择标准来选择具有高潜在谷物蛋白质百分比的品系。能够在其营养组织中储存大量 N 并在开花期获得高 NNI 值的品种，如 Aureo，在确定潜在粒数期间的 RUE 方面受到惩罚。