Since 1940 molybdenum has been known as an essential trace element in plant nutrition and physiology. It has a central role in nitrogen metabolism, and its deficiency leads to nitrate accumulation in plants. In this study, we cultivated maize seedlings (Zea mays L. cv. Norma SC) in nutrient solution and soil (rhizoboxes) to investigate the effect of molybdenum treatment on the absorption of molybdenum, sulphur and iron. These elements have been previously shown to play important roles in nitrate reduction, because they are necessary for the function of the nitrate reductase enzyme. We also investigated the relationship between molybdenum treatments and different nitrogen forms in maize. Molybdenum treatments were 0, 0.96, 9.6 and 96 μg kg-1 in the nutrition solution experiments, and 0, 30, 90, 270 mg kg-1 in the rhizobox experiments. On the basis of our results, the increased Mo level produced higher plant available Mo concentration in nutrient solution and in soil, which resulted increased concentration of Mo in shoots and roots of maize seedlings. In addition it was observed that maize seedlings accumulated more molybdenum in their roots than in their shoots at all treatments. In contrast, molybdenum treatments did not affect significantly either iron or sulphur concentrations in the plant, even if these elements (Mo, S and Fe) play alike important roles in nitrogen metabolism. Furthermore, the physiological molybdenum level (1x Mo = 0.01 µM) reduced NO3-N and enhanced the NH4-N concentrations in seedlings, suggesting that nitrate reduction was more intense under a well-balanced molybdenum supply.

No abstract

No abstract

Molybdenum is not a well-known microelement, but being a constituent of several important cellular enzymes it is an essential microelement. Molybdenum occurs in all foods, but at very low levels. There does not appear to be any particular foods or types of foods, which in the absence of extrinsic factors, naturally have high levels of molybdenum. However, environmental pollution, from natural or anthropogenic sources, can lead to high level of the metal in plants.Our study is based on the long-term field experiments of Nagyhörcsök, where different levels of soil contamination conditions are simulated. Soil and plant samples were collected from the experiment station to study the behaviour of molybdenum: total concentration, available  concentration, leaching, transformation, uptake by and transport within the plants, accumulation in different organs, phytotoxicity and effects on the quantity and quality of the crop. In this work we present the results of maize and peas and the soil samples related to them.According to our data molybdenum is leaching from the topsoil at a medium rate and it appears in the deeper layers. In the case of plant samples we found that molybdenum level in the straw is many times higher than that is in the grain, so molybdenum accumulates in the vegetative organs of the plant. The data also show differences in the molybdenum-uptake of cereals and Fabaceae (or Leguminosae).