Molybdenum in the Environment
Molybdenum in the Biosphere
Molybdenum in plants
Molybdenum is an essential micronutrient for plant growth and for microsymbionts. Even when the total Mo content of the soil is sufficient, since Mo is often sequestered by Fe- or Al-oxohydroxides, especially in acidic soils, the concentration of the water-soluble molybdate anion available for uptake by plants may be limiting for the plant. No specific molybdenum uptake system is known for plants, but since molybdate and sulfate behave similarly and have similar structure, uptake of molybdate could be mediated unspecifically by one of the sulfate pathways.
Zimmer, W, Mendel, R, Molybdenum metabolism in plants, Plant Biology, 999,1, 160-168.
Molybdenum concentrations in various plants
| Source |
Concentration /ppm dry weight |
| Land Plants |
0.9 |
| Plankton |
1.0 |
| Brown Algae |
0.45 |
| Bryophytes |
0.7 |
| Ferns |
0.8 |
| Gymnosperms |
0.13 |
| Angiosperms |
0.9 |
| Fungi |
1.5 |
| hay [2] |
0.78 |
| citrus leaves [2] |
0.14 |
[1] Bowen, H. J. M., Trace Elements in Biochemistry, 1966, Academic Press, N. Y.
[2] Alonso, J.I.G., Camblor, M.G., Bayon, M.M., Marchante Gayon, J.M., Sanz Medel, A., Different quantification approaches for the analysis of biological and environmental samples using inductively coupled plasma mass spectrometry, Journal Of Mass Spectrometry, 1997, 32, 556-564.
Tobacco 0.3 – 1.76 microg Mo/g
Voss, R.C., Nicol, H., Metallic trace elements in tobacco, Lancet, 1960, 2, 435 – 436.
Concentrations of barium (Ba), calcium (Ca), Cu, iron (Fe), K, magnesium (Mg), manganese (Mn), molybdenum (Mo), sodium (Na), rubidium (Rb), strontium (Sr), and zinc (Zn) in leaf and stem tissues were correlated with treatment and tissue. Generally, increasing Cu resulted in elevated Ba, Fe, Mo, and Sr as well as Cu levels.
The presence of peat resulted in reduced levels, generally in both leaf and stem, of Ba, Mg, Mn, Rb, and Zn and increased levels of Fe, K, and Mo.
Elemental concentrations were higher in leaf tissue rather than stem, with the exceptions of Na and Zn.
Elemental concentration ranges, over all tissues and conditions of added Cu and peat were (mg kg-1) Ba 9-49, Ca 6380-16340, Cu 2-11, Fe 10-57, K 4070-16950, Mg 900-4260, Mn 22-197, Mo 0.02-0.19, Na 28-124, Rb 0.7-12, Sr 41-58, Zn 18-48
Ihnat, M., Neilsen, G. H., and Hogue, E. J., Elemental content relationships in greenhouse grown apple seedlings supplemented with copper and peat, Communications in Soil Science and Plant Analysis, 2000, 31, 803-825.
Tropical grasses
Mo 0.02-1.23 mg kg-l dry matter
Youssef, F.G., McDowell, L.R., Brathwaite, R.A.I., The status of certain trace minerals and sulphur of some tropical grasses in Trinidad, Tropical Agriculture, 1999, 76, 57-62.
Molybdenum in plants uptake and accumulation
Molybdenum is utilized by selected enzymes to carry out redox reactions. Enzymes that require molybdenum for activity include nitrate reductase, xanthine dehydrogenase, aldehyde oxidase and sulfite oxidase. Loss of Mo-dependent enzyme activity (directly or indirectly through low internal molybdenum levels) impacts upon plant development, in particular, those processes involving nitrogen metabolism and the synthesis of the phytohormones abscisic acid and indole-3 butyric acid. It is unclear how plants access molybdate from the soil solution or later redistribute it once in the plant. Plants have similar physiological molybdenum transport phenotypes to those found in prokaryotic systems. Analysis of prokaryotic molybdate transport mechanisms and anion transport mechanisms in plants will help our understanding of how molybenum is accumulated.
Kaiser, B.N., Gridley, K. L., Brady, J. N., Phillips, T., and Tyerman, S. D., The role of molybdenum in agricultural plant production, Annals of Botany, 2005, 96, 745-754.
Molybdenum concentration varies with location and species: for example, in pastures in different areas molybdenum concentrations varying from 0.1 to 200 ppm dry weight have been reported [Underwood, 1962; Kolomiitseva et al., 1970].
Underwood, E. J., Trace Elements in Human and Animal Nutrition, 2nd Ed. 1962, 100. Academic Press, London.
Kolomiitseva, M. G., Polonskaya, M. N. and Osipov, G. K.,Mikroelem. Sel. Khoz. Med., 1968, 4, 183;
Warren, H . V., Delavault, R. E., Fletcher, K. W., Geology Environ. Contr. Bull., 1971, 6, 34.
U.S Department of the Interior, 1967, 1968, 1970
Sequi, P., Agrochimica, 1972 (Publ. 1973), 17, 119
Webb, J. S., Geol. Soc. Amer., Mem., 1971, 123, 31.
Ivanova, N. N., Agrochimica, 1972 (Publ. 1973), 17, 96.
Mo in plants grown on a landfill site
The mean concentrations (microg/g dry weight) of Se and Mo in the shoots of plants grown on a landfill site did not exceed, respectively,
0.12 (Se) and 18.7 (Mo) in bird's-foot trefoil (Lotus corniculatus L.),
0.06 and 12.1 in red clover (Trifolium pratense L.),
0.07 and 5.3 in timothy (Phleum pratense L.),
0.09 and 2.2 in a mixture of grasses.
These concentrations were greater than those in the same species harvested concurrently from a non-landfill site.
Molybdenum uptake in plants
The uptake of Mo is induced by NO3- and inhibited by sulfate.
W. Reid, R.J., Mechanisms of micronutrient uptake in plants, Australian Journal of Plant Physiology, 2001, 28, 659-666.
When supplied with molybdate Indian mustard (Brassica juncea) seedlings accumulated water-soluble blue crystals in their peripheral cell lavers. A mutant without anthocyanin did not show accumulation of a blue molybdenum compound. Mo appears to be sequestered in vacuoles of the peripheral cell layers of Brassica spp. as a blue compound, probably a Mo-anthocyanin complex.
Hale, K.L., McGrath, S. P., Lombi, E., Stack, S. M., Terry, N., Pickering, I. J., George, G. N., and Pilon-Smits, E. A. H., Molybdenum sequestration in Brassica species. A role for anthocyanins?, Plant Physiology, 2001, 126, 1391-1402.
Mo absorption by cress
Mo is readily absorbed both into cress (Lepidium sativum) and into french beans (Phaseolus vulg. var. nanus) [Giussani et al., 1998]. For cress grown from seeds in Petri dishes on blotter paper moistened with tap water solutions of molybdate of different concentrations, the Mo content increased linearly with time before harvesting and with the molybdate concentration.
Giussani, A., Heinrichs, U., Roth, P., Werner, E., Schramel, P., Wendler, A., Biokinetic studies in humans with stable isotopes as tracers. Part 1: A methodology for incorporation of trace metals into vegetables, Isotopes In Environmental And Health Studies, 1998, 34,291-296.
Mo in sugarcane leaves
In crops of the sugarcane, the concentrations of molybdenum (Mo) in the leaves are generally lower than 0.3 mg Mo kg-1 . These low concentrations have resulted in limitations in the methods and instruments that can be used for these analyses. The objective of this study was to evaluate three different techniques to determine the concentration of Mo in sugarcane leaves sampled in the principal sugarcane-producing areas in Brazil. Two spectrometric techniques were evaluated by using ICP-EAS (Inductively Coupled Plasma-Emission Automated System) and DCP-MEAS (Direct Coupled Plasma-Multiple Emission Automated System) and a colorimetric technique of the reaction between potassium iodide and hydrogen peroxide (KI-H2O2). The techniques ICP-EAS and KI-H2O2 produced results of satisfactory accuracy and precision, whereas the DCP-MEAS consistently overestimated the Mo concentrations in cane leaves. The KI-H2O2 technique showed sensitivity 5 times greater than the ICP-EAS, with minimum detection limits of 0.1 and 0.5 mg Mo kg-1 , respectively
Polidoro, J. C., Medeiros, A. F. A., Xavier, R. P., Medeiros, J. A., Boddey, R. M., Alves, B. J. R., and Urquiaga, S., Evaluation of techniques for determination of molybdenum in sugarcane leaves, Communications in Soil Science and Plant Analysis, 2006, 37, 77-91.
Molybdenum uptake and transport in plants
The molybdenum concentration in the sap was approximately 11 times greater in the absence of sulfate in the nutrient medium. Restoring sulfate to the nutrient medium without sulfur depressed the Mo concentration of the sap at the next harvest to a value similar to that in plants receiving sulfate from the onset of the growth period and, similarly, raised the S concentration as well. Sulfate and molybdate compete for the same carrier and transport sites in uptake, and sulfate deficiency leads to excess Mo uptake.
Alhendawi, R.A., Kirkby, E. A., and Pilbeam, D. J., Evidence that sulfur deficiency enhances molybdenum transport in xylem sap of tomato plants, Journal of Plant Nutrition, 2005, 28, 1347-1353.
Molybdate transport in plants
A molybdate transporter, ‘MOT1’, has been identified from the plant Arabidopsis thaliana. The following is a summary of the paper. The reader is recommended to consult the original paper and key references for methods and justifications.
MOT1 is expressed in both roots and shoots. The MOT1 protein is localized, in part, to plasma membranes and to vesicles. MOT1 enhances molybdate uptake from soil into root cells for utilization and also for translocation to shoots. MOT1 is required for efficient uptake and translocation of molybdate and for normal growth under conditions of limited molybdate supply. MOT1 is a high-affinity Mo transporter. The high molybdate affinity of MOT1 enables plants to obtain scarce molybdate from soil.
MOT1 is also specific for molybdate (as opposed to sulfate).
The affinity of MOT1 for molybdate was determined from kinetic studies in yeast of uptake of molybdate (applied as ammonium heptamolybdate) vs time. For time-course analysis of molybdate uptake, cells were transferred to the medium supplemented with 24 nM ammonium heptamolybdate, and shaken at 30°C for 0, 5, 10, 15, 20, 30, 45, or 60 min. For kinetic analysis of molybdate uptake cells were transferred to the medium supplemented with 7, 8, 10, 12, 16, 24, 97 or 194 nM ammonium heptamolybdate, and shaken at 30 °C for 15 min.
The stationary level of molybdenum concentration in cells expressing MOT1 was roughly 30 microM; more than 100-fold higher than that in the medium used for the uptake study. Thus MOT1 is a molybdate transporter capable of transporting molybdate against a concentration gradient.
Analysis of the kinetics of molybdate uptake (Lineweaver–Burk plot) by yeast expressing MOT1 gave Km 21 ± 4 nM and Vmax 0.5 ±0.1 microg_g-1DW min-1 where Km, the Michaelis constant, is the dissociation constant of a MOT1-molybdate complex and Vmax is the maximal uptake velocity. The authors comment that 20 nM is the lowest reported Km value of the mineral–nutrient transporters in plants.
So MOT1 is well described as a high-affinity molybdate transporter.
The genetic mechanism that controls Mo concentration in Arabidopsis thaliana shoots, was studied in detail. The trait is mostly regulated by a single locus on chromosome 2 in a region containing a gene (At2g25680) annotated as Sultr5;2 (representing a member of the sulfate transporter group). At2g25680 was identified as a molybdate transporter by studying the molybdate uptake of Arabidopsis thaliana mutant lines (mot1-1 and mot1-2 having modified At2g25680) grown in the presence of 170 nM molybdate for five weeks, after which the molybdenum concentrations in shoots and roots were determined. The molybdenum concentrations in shoots of the mot1-1 and mot1-2 mutant plants were reduced to 10% and 20% of that in the wild type, and, in roots, the molybdenum concentrations were reduced to 20% and 25% of that in the wild type. Thus At2g25680 (named MOT1) is the determinant of the Mo concentration in both roots and shoots.
Tomatsu, H., Takano, J., Takahashi, H., Watanabe-Takahashi, A., Shibagaki, N., and Fujiwara, T., An Arabidopsis thaliana high-affinity molybdate transporter required for efficient uptake of molybdate from soil, Proceedings of the National Academy of Sciences of the United States of America, 2007, 104, 18807-18812.
Molybdenum in pastures and herbage
Pasture
Concentrations in normal herbage may range from 0.1 to 0.3 ppm on a dry matter basis. The molybdenum is present as soluble ammonium molybdate, insoluble molybdenum trioxide, calcium molybdate and molybdenum disulfide. In areas of high industrial activity herbage values of up to 231 ppm have resulted. The differential in the molybdenum concentration of soils due to pH could result in differing levels due to the consumption of herbage grown in soils of regional type.
Gardner, A. W. and Hall-Patch, P. K., J. Nutr. , 1962, 84, 31.
Some soils may require supplemental molybdenum. These include soils low in organic matter, severely eroded or heavily weathered soils, soils low in total molybdenum, sandy soils, soils high in iron, and acid soils (pH <6.3). Molybdenum is not readily absorbed by plants from acid soils and liming or addition of molybdenum is required to increase the molybdenum concentration in pasture. Some plants exhibit visual symptoms of molybdenum deficiency, e.g., the classic whiptail in cauliflower and yellow spot in citrus, but often visual symptoms of molybdenum deficiency are not present or appear as symptoms of nitrogen deficiency. A typical supplemental molybdenum addition for legumes is approximately 0.25 kg molybdenum per acre. Molybdenum can be applied in fertilisers, by seed treatment or foliar sprays.
Some pastures have exceptionally high concentrations of molybdenum (generally associated with alkaline soils), and may give rise to symptoms of molybdenum toxicity in sheep and cattle. Guideline values of up to 50 mg/kg dry weight have been fixed for molybdenum concentrations in agricultural soils [Hornick et al., 1977]. A higher incidence of uratic diathesis was reported from a locality in Armenia where the soil was found to contain 77 mg/kg of molybdenum and 39 mg/kg of copper. The total daily intake of molybdenum and copper in the adults of this area were estimated to be 10 times that of an adult in a control area [Kovalskij et al., 1961; ILO Geneva, 1980].
Hornick, S. B., Baker, D. E. and Guss, S. B., Molybdenum in the Environment, 1977, 2, Marcel Dekker, New York.
Kovalskij, V. V., Jarovaja, G. A. and Smavonjan, D. M., Z. Obsc. Biol., 1961, XII, 179.
ILO Geneva, 1980.
Molybdenum in Bacteria
Comparative analysis of the molybdate transport proteins in various bacteria and archaea is reviewed. Molybdate is transported by an ABC-type transporter comprising three proteins, ModA (periplasmic binding protein), ModB (membrane protein) and ModC, the ATPase. In the absence of the high-affinity molybdate transporter, molybdate is also transported by another ABC transporter which transports sulfate/thiosulfate as well as by a nonspecific anion transporter.
Self, W.T., Grunden, A. M., Hasona, A., and Shanmugam, K. T., Molybdate transport, Research in Microbiology, 2001, 152, 311-321.
Antimicrobial properties of ketimine molybdenum(VI) complexes
Dioxomolybdenum(VI) and oxovanadium(V) complexes of
heterocyclic ketimines, 5-nitro-3-(indolin-2-one)hydrazinecarbothioamide,
5-nitro-3-(indolin-2- one) hydrazinecarboxamide , 6-nitro-3-(indolin-2-one)
hydrazinecarbo- thioamide and 6-nitro3-(indolin-2-one) hydrazinecarboxamide
were applied to pathogenic bacteria and fungi to assess their growth inhibition
potency.
Garg, R., Fahmi, N., and Singh, R. V., Synthetic, spectral, and antimicrobial aspects of biologically relevant coordination compounds of dioxomolybdenum(VI) and oxovanadium(V), Russian Journal of Coordination Chemistry, 2008, 34, 198-203.
Molybdenum in animals
| Source |
Concentration / |
| Marine Animals |
0.6 - 2.5 |
| Coelenterates |
0.7 |
| Molluscs |
2.0 |
| Echinoderms |
2.5 |
| Crustacea |
0.6 |
| Insects |
0.6 |
| Fish |
1.0 |
| Mammals |
<1.0 |
| Bone |
<2.6 |
Bowen, H. J. M., Trace Elements in Biochemistry, 1966, Academic Press, N. Y.
| Animal |
Brain |
Kidney |
Liver |
Lung |
Muscle |
Spleen |
| Adult rat |
0.24 |
1.0 |
1.8 |
0.37 |
0.06 |
0.52 |
| Chicken |
- |
4.4 |
3.6 |
- |
0.14 |
- |
| Seaducks Southeast Alaska [4] |
|
<10 |
<10 |
|
|
|
| bovine [5] |
|
|
3.62 |
|
|
|
| horse [5] |
|
2.20 |
|
|
|
|
Concentrations in ppm Mo on dry weight basis.
[2] (a) Underwood, E. J.,Trace Elements in Human and Animal Nutrition, 1962, 2nd Ed. Academic Press, London, 100; (b) Kolomiitseva, M. G., Polonskaya, M. N. and Osipov, G. K., Mikroelem. Sel. Khoz. Med., 1968, 4, 183; (c) Schroeder, H. A., Balassa, J. J. and Tipton, I. H., J. Chronic Diseases, 1970, 23, 481.
[3] Tipton I. H. and Cook, M.J., Health Phys., 1963, 9, 103.
[4] Franson, J.C., Koehl, P.S., Derksen, D.V., Rothe, T.C., Bunck, C.M., Moore, J.F., Heavy-Metals In Seaducks And Mussels From Misty-Fjords-National-Monument In Southeast Alaska, Environmental Monitoring And Assessment, 1995, 36,149-167.
[5] Alonso, J.I.G., Camblor, M.G., Bayon, M.M., Marchante Gayon, J.M., Sanz Medel, A., Different quantification approaches for the analysis of biological and environmental samples using inductively coupled plasma mass spectrometry, Journal Of Mass Spectrometry, 1997, 32, 556-564.
Molybdenum in Pig liver and mussels
Molybdenum concentrations were:
pig liver 3.8 – 4.0 microg/g
mussel 0.60 – 0.63 microg/g
Jiang, C.Q., Wang, J. Z., and He, F., Spectrofluorimetric determination of trace amounts of molybdenum in pig liver and mussels, Analytica Chimica Acta, 2001, 439, 307-313.
Molybdenum tolerance of sheep, cows, horses and pigs
Sheep and cows, develop adverse reactions to feed containing 2-30 ppm molybdenum; horses and pigs tolerate feed with concentrations > 1000 ppm molybdenum.
Smyth, H.E., Hygienic standard for daily inhalation. Ind Hyg Q, 1956, 17,129-185.
Molybdenum deficiency and elevated xanthine and sulfite
Molybdenum deficiency may lead to amino acid intolerance, irritability, elevated urinary xanthine and sulfite, and reduced uric acid and sulfate. Condition cured by 160 microg Mo/d administered.
Aburnrad NN, Schneider AJ, Steel D, Rogers LS. Amino acid intolerance during prolonged total parenteral nutrition reversed by molybdate therapy. Am J Clin Nutr 198 ; 34:2551-2559.
Molybdenum and insulin in rats
Insulin resistance, hyperinsulinemia, hypertriglyceridemia and hypertension occur in rats fed with high fructose diet. Sodium molybdate has insulin-like effects in animal models of type I and type II diabetes. The effects of Mo on fructose- hypertensive male Wistar rats was investigated. Molybdate treatment prevented fructose- induced hyperinsulinemia and hypertension in rats
Guner, S., Tay, A., Altan, V. M., and Ozcelikay, A. T., Effect of sodium molybdate on fructose-induced hyperinsulinemia and hypertension in rats, Trace Elements and Electrolytes, 2001, 18, 39-46.
| Source |
Mo/mg/kg wet |
| clams hardshell |
0.16+/- 0.33 |
| clams softshell |
0.31+/-0.38 |
| oysters Eastern |
0.08+/-0.24 |
| oysters Pacific |
below detection |
Baseline values for elements in clams and oysters harvested from US coastal waters 1985/1986.
Capar, S.G., Yess, N.J., US Food-And-Drug-Administration Survey Of Cadmium, Lead And Other Elements In Clams And Oysters, Food Additives And Contaminants, 1996,13,553-560.
| Source of liver |
Cu/mg/kg wet |
Mo/mg/kg wet |
| Aborted horse fetus |
3.74 |
1.61 |
| Dead horse |
4.35 |
1.69 |
| Slaughtered cow |
1.10 |
1.38 |
| Control cow |
17.7 |
1.37 |
Fly ash used in road construction blew over and contaminated pasture and water. The fly ash pH was ca 10 giving high bioavailabilityof Mo. Mo in forage 6 months after fly ash contamination 1.2mg Mo/kg dry weight (cf ‘normal’ in grasses in Denmark 0.1 - 0.3), Cu 5.0 mg Cu/kg.
Biological half life of Mo in cattle 24 h. Mo in fly ash 7 - 160 mg/kg . Absorption of Mo from gastrointestinal tract of ruminants 80 %, from humans and horses (?) 5 - 72%.