Lettuce is one of the most popular vegetables, and the market niche of the baby leaf variety is expanding. The manner in which nitrogen (N) is supplied and the available concentration of the micronutrient molybdenum (Mo) affect N metabolism, with reflects on the nutritional quality of that vegetable. Here, two Mo concentrations (0.06 and 0.12 mg/L) and four proportions (%) of nitrate (NO3 - )/ammonium (NH4 + )(100/0, 75/25, 50/50, and 25/75) were supplied to hydroponic baby leaf lettuce floating type to evaluate their effects on plant growth and leaf mineral and NO3 - compositions. Shoot dry mass did not differ among the different treatments, although fresh mass was lower in treatments with larger proportions of NH4 + . Higher leaf concentrations of NO3 - were observed in plants treated with 100% N-NO3 - , but they were still below tolerable limits for human health. The enzyme nitrate reductase was not found to be sensitive to the nitrogen sources or to Mo concentrations. N proportions and Mo concentrations differently affected macro- (C, N, P, K, Ca, Mg, and S) and micronutrients (Cu, Fe, Mn, Mo, and Zn) leaf concentrations. Although treatment with 100% N-NO3 - favored higher mineral concentrations in lettuce leaves, the addition of 25% N-NH4 + allowed fresh mass production with the lowest NO3 - concentrations. As such, and considering the healthy reduction of NO3 - consumption by humans and the maintenance of plant productivity, the 75/25 NO3 - /NH4 + proportion is recommended for the hydroponic cultivation of baby leaf var. Mimosa lettuce. PRACTICAL APPLICATION: We demonstrate a direct link between the constitution of nutrient solution with nitrate accumulation by hydroponic lettuce and indicate the best source of N as well as the concentration of Mn to healthy reduction of NO3 - consumption by humans and the maintenance of plant productivity.

中文翻译：

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氮源和钼会影响水培小生菜的营养质量和硝酸盐浓度吗？

生菜是最受欢迎的蔬菜之一，幼叶品种的市场利基正在扩大。氮 (N) 的供应方式和微量营养素钼 (Mo) 的可用浓度影响氮代谢，反映了该蔬菜的营养品质。这里，两种 Mo 浓度（0.06 和 0.12 mg/L）和四种比例（%）的硝酸盐 (NO3 - )/铵 (NH4 + )（100/0、75/25、50/50 和 25/75）分别为提供给水培幼叶生菜漂浮型，以评估它们对植物生长和叶片矿物质和 NO3 - 成分的影响。尽管在NH4 + 比例较大的处理中新鲜质量较低，但不同处理之间的芽干质量没有差异。在用 100% N-NO3 - 处理的植物中观察到更高的 NO3 - 叶浓度，但它们仍低于人类健康的可容忍限度。未发现硝酸还原酶对氮源或钼浓度敏感。N 比例和 Mo 浓度对宏观（C、N、P、K、Ca、Mg 和 S）和微量营养素（Cu、Fe、Mn、Mo 和 Zn）叶片浓度的影响不同。尽管用 100% N-NO3 - 处理有利于生菜叶子中更高的矿物质浓度，但添加 25% N-NH4 + 允许以最低的 NO3 - 浓度进行新鲜大规模生产。因此，考虑到人类对 NO3 - 消耗的健康减少和植物生产力的维持，建议将 75/25 NO3 - /NH4 + 比例用于幼叶变种的水培栽培。含羞草生菜。实际应用：