Department of Plant Biology and Ecology, Faculty of Pharmacy, University of the Basque Country UPV/EHU, E-01006, Vitoria-Gasteiz, Spain; Laboratory of Plant Molecular Biology, Institute of Biophysics AS CR, CEITEC - Central European Institute of Technology, Phytophthora Research Centre, Faculty of Agronomy, Mendel University in Brno, Zemědělská 1, CZ-613 00, Brno, Czech Republic.
Department of Plant Biology and Ecology, Faculty of Pharmacy, University of the Basque Country UPV/EHU, E-01006, Vitoria-Gasteiz, Spain; Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 27, CZ-783 71, Olomouc, Czech Republic.
Plant Physiol Biochem. 2017 Nov;120:213-222. doi: 10.1016/j.plaphy.2017.10.006. Epub 2017 Oct 12.
Nitrogen (N) is an important regulator of photosynthetic carbon (C) flow in plants, and an adequate balance between N and C metabolism is needed for correct plant development. However, an excessive N supply can alter this balance and cause changes in specific organic compounds associated with primary and secondary metabolism, including plant growth regulators. In previous work, we observed that high nitrate supply (15 mM) to maize plants led to a decrease in leaf expansion and overall biomass production, when compared with low nitrate supply (5 mM). Thus, the aim of this work is to study how overdoses of nitrate can affect photosynthesis and plant development. The results show that high nitrate doses greatly increased amino acid production, which led to a decrease in the concentration of 2-oxoglutarate, the main source of C skeletons for N assimilation. The concentration of 1-aminocyclopropane-1-carboxylic acid (and possibly its product, ethylene) also rose in high nitrate plants, leading to a decrease in leaf expansion, reducing the demand for photoassimilates by the growing tissues and causing the accumulation of sugars in source leaves. This accumulation of sugars, together with the decrease in 2-oxoglutarate levels and the reduction in chlorophyll concentration, decreased plant photosynthetic rates. This work provides new insights into how high nitrate concentration alters the balance between C and N metabolism, reducing photosynthetic rates and disrupting whole plant development. These findings are particularly relevant since negative effects of nitrate in contexts other than root growth have rarely been studied.
氮（N）是植物光合作用碳（C）流的重要调节因子，N 和 C 代谢之间需要适当的平衡才能正确发育植物。然而，过量的 N 供应会改变这种平衡，并导致与初级和次级代谢相关的特定有机化合物发生变化，包括植物生长调节剂。在之前的工作中，我们观察到，与低硝酸盐供应（5 mM）相比，高硝酸盐供应（15 mM）会导致玉米植株叶片扩展和整体生物量生产减少。因此，本研究的目的是研究硝酸盐过量如何影响光合作用和植物发育。结果表明，高硝酸盐剂量大大增加了氨基酸的产生，导致 N 同化的 C 骨架主要来源 2-酮戊二酸的浓度降低。高硝酸盐植物中的 1-氨基环丙烷-1-羧酸（及其产物乙烯）的浓度也升高，导致叶片扩展减少，减少生长组织对光产物的需求，并导致源叶中糖的积累。这种糖的积累，加上 2-酮戊二酸水平的降低和叶绿素浓度的减少，降低了植物的光合速率。这项工作提供了新的见解，即高硝酸盐浓度如何改变 C 和 N 代谢之间的平衡，从而降低光合速率并破坏整个植物的发育。由于很少研究硝酸盐在根系生长以外的环境中的负面影响，因此这些发现尤为重要。
