Field studies on the interaction of mineral nitrogen supply and free air CO2 enrichment on grain protein content and grain protein composition of winter wheat

大气CO2浓度（[CO2]）的升高促进小麦生长和产量，但通过降低籽粒中的面筋浓度从而影响籽粒蛋白质浓度（GP%），从而影响烘焙品质。CO2对谷物品质的负面影响的原因仍在争论中。据讨论，GP%的下降，在升高[CO2]的结果，从生长稀释，因为增加的粮食干重高于增加的N吸收。此外，它是讨论了升高[CO2]可能会减少氮的收购。籽粒中最大量的氮来自开花前积累在营养组织中的有机氮的再调动。一小部分是由于氮的转移，这是同化开花和籽粒成熟之间。在这项研究中，[CO2]使用自由空气CO2富集（FACE）和三个水平的无机氮供应（60-350公斤氮公顷-1）对氮的再动员和转运，并对籽粒蛋白质的浓度和组成的影响将进行调查。N的再动员将从叶和茎的干重以及开花期和籽粒成熟期之间的N浓度差异来量化。它将被检查是否升高[CO2]减少N再动员在低N供应由于茎部分的增加和叶N浓度的降低。利用15 N标记花期增施的氮肥，研究CO2浓度升高对氮素运转的影响，特别是在中等施氮水平下。我们将测试是否可以通过使用非常高的氮肥水平来防止CO2导致的GP%的下降。在所有这些实验中，将使用固体硝酸铵钙。在另一项试验中，将仅使用硝酸盐氮，向植物提供常规水平的氮肥（180 kg ha-1）。本研究的目的是确定是否[CO2]升高对小麦的氮吸收，生长和GP%的影响强烈影响的N-形态。除了植物生长测量外，还将记录环境条件，以便以后使用这些数据来模拟气候变化下的植物生长和谷物质量。

The rise of the atmospheric CO2 concentration ([CO2]) improves wheat growth and yield but affects grain protein concentration (GP%) by decreasing gluten concentration in the grain and thus baking quality. The reasons for the negative CO2-effect on grain quality are still under debate. It is discussed that the decrease of GP% under elevated [CO2] results from growth dilution since the increase in grain dry weight is higher than the increase in N acquisition. Furthermore it is discussed that elevated [CO2] may reduce N acquisition. The largest amount for grain N comes from the remobilization of organic N accumulated in the vegetative tissue until anthesis. A smaller part is attributed to the translocation of N which is assimilated between anthesis and grain maturity. In this study the effects of elevated [CO2] using free air CO2 enrichment (FACE) and three levels of mineral nitrogen supply (60-350 kg N ha-1) on nitrogen remobilization and translocation and on concentration and composition of grain protein will be investigated. Remobilization of N will be quantified from the dry weights of the leaves and stems and the difference in N concentration between anthesis and grain maturity. It will be examined whether elevated [CO2] decreases N remobilization at low N supply due to an increase of the stem fraction and a decrease of the leaf N concentration. 15N labeling of the N fertilizer added at flowering will be used to investigate whether CO2 enrichment affects N translocation especially at medium level of N fertilization. We will test whether the decrease in GP% by CO2 can be prevented by using a very high level of N fertilization. In all these experiments solid calcium ammonium nitrate will be used. In an additional experiment plants will be supplied with a usual level of N fertilization (180 kg ha-1) by using only nitrate-N. The objective of this study is to determine whether the effect of elevated [CO2] on N uptake, growth and GP% of wheat is strongly influenced by the N-form. Beside plant growth measurements environmental conditions will be recorded enabling the later use of the data for modelling plant growth and grain quality under climate change.