The purpose of the present work was to study the effect of the nitrogen source (NO3- vs NH4+) on cadmium (Cd) uptake, translocation and partition and its associated toxicity in hydroponically-grown Arabidopsis plants. After a short growth period on a complete Hoagland nutrient solution, Arabidopsis seedlings continued in the same growth medium (NA) or were switched to NO3- (N) or NH4+ (A) as sole N sources and supplied with 2.5 μM Cd. Unrelated to the nitrogen source, Cd reached higher levels in roots than in leaves. However, when ammonium was the source of nitrogen, Cd accumulation in roots was lower than in N or NA medium and the metal translocation to the aerial part was restricted, reaching values 25%-35% below the levels observed in plants grown with N or NA. Cadmium negatively affected chlorophyll content and PSII quantum yield, independently of the nitrogen source, with the highest decrease (35%) under NA treatment. Proline content increased, either with NA, N or A supplied in the presence of Cd, whereas a rise in total anthocyanin content was clearly favored when ammonium was the source of nitrogen, with or without Cd. In leaves, while NIA1 and NIA2 expression was markedly reduced by Cd in the presence of N or NA, ammonium source slightly reduced NIA1 expression but greatly upregulated NIA2 expression upon Cd exposure. The decay in NR activity was independent of the nitrogen source when Cd was applied and this decay was accompanied by a great increase in NH4+ levels either with nitrates or ammonium in the medium in the presence of Cd. Only NIA1 was detected in roots and its expression, together with NR activity and nitrates levels, was the highest in N medium devoid of Cd. The possibility of reducing Cd health risks through nitrogen fertilization practices is discussed.

中文翻译：

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氮源会影响拟南芥植物中镉的分布吗？

本工作的目的是研究水培拟南芥中氮源（NO3-vs NH4 +）对镉（Cd）吸收，转运和分配及其相关毒性的影响。在完整的Hoagland营养液中短暂生长后，拟南芥幼苗在相同的生长培养基（NA）中继续生长，或转换为NO3-（N）或NH4 +（A）作为唯一的N源，并提供2.5μMCd。与氮源无关，镉在根中的含量高于在叶片中的含量。但是，当铵盐是氮的来源时，根中的Cd积累要低于N或NA介质，并且金属向地上部的迁移受到限制，其值比N或NA种植的植物低25％-35％。不适用 镉对叶绿素含量和PSII量子产率产生负面影响，与氮源无关，在NA处理下减少量最大（35％）。在有Cd的情况下提供NA，N或A时，脯氨酸的含量都会增加，而以铵为氮源（有或没有Cd的情况下）时，总花青素含量的增加显然是有利的。在叶片中，尽管在N或NA的存在下Cd会显着降低NIA1和NIA2的表达，但铵离子源会稍微降低NIA1的表达，但在镉暴露后大大上调NIA2的表达。施用镉后，NR活性的降低与氮源无关，并且在镉存在下，培养基中硝酸盐或铵的NH4 +含量大大增加。在根部及其表达中仅检测到NIA1，以及NR活性和硝酸盐水平，在不含镉的氮培养基中最高。讨论了通过氮肥施用减少镉健康风险的可能性。