The biological and toxicological importance of molybdenum in the environment and in the nutrition of plants, animals and man

In 1930, Bortels showed that molybdenum is necessary for nitrogen fixation in Acetobacter, and in 1939 Arnon and Stout reported that molyb denum is essential for life in higher plants. Nitrogenase is the nitrogen-fixing enzyme complex, while nitrate reductase requires molybdenum for its activity. Molybdenum occurs in the earth crust with an abundance of 1.0–1.4 mg/kg. The molybdenum content of the vegetation is determined by the amount of this element in the soil and its pH-value. The weathering soils of granite, porphyry, gneiss and Rotliegendes produce a molyb denum-rich vegetation. Significantly poorer in Mo is the vegetation on loess, diluvial sands, alluvial riverside soils and especially on Keuper and Muschelkalk weathering soils, which produce legumes and, e.g. cauliflower with molybdenum deficiency symptoms. The molybdenum content of the flora decreases with increasing age. Legumes store the highest molybdenum levels in the bulbs of their roots; on average, they accumulate more molybdenum than herbs and grasses do. The danger of molybdenum toxicity in plants is small