Molybdenum in plants

I hope you enjoy the subject of molybdenum (Mo, atomic number 42, transition metal, group 6 and fifth period in the periodic classification, Nox ranging from 6 to -2).

Whether you see any errors, or having suggestions and doubts, please feel free to be in contact.

Molybdenum is required in small amounts by plants (micronutrient), for example, while the concentration of nitrogen in the dry matter of the plants is 1000 mmol / kg, the concentration of Mo is 0.001 mmol / kg.

However Mo is part of cofactors that bind nitrate reductase and nitrogenase. These two enzymes are crucial for the assimilation of nitrogen by plants.


Three-dimensional structure of nitrate reductase


Nitrate reductase converts the nitrate that has been absorbed from the soil to nitrite which will later be converted to ammonium. Ammonium will be converted to glutamate by the GS-GOGAT path. Henceforth several amino acids can be formed. Nitrogenase is an enzyme found in bacteria that live in symbiosis in the roots of some plant families, the most famous family being the legumes (Fabaceae), soybeans and beans. In few words, nitrogenase reduces atmospheric nitrogen in ammonia. These bacteria supply nitrogen to plants in exchange for carbon.


Nitrate Reductase Cofactor



Mo is assimilated by plants in the form of the molybdate anion, which is more "available" for plants in basic pH situations, but in situations of lower pH, below of 6 or 5, Mo availability is very low while most other micronutrients have good availability in this range.

Even in the preparation of fertilizers with micronutrients, if the solution is acidic to maintain the solubility of the other micronutrients, it can promote the precipitation of molybdate, which is not good. Therefore, many fertilizers with formulations containing molybdenum are sold separately, sometimes with boron which presents only slightly similar behavior (see table below).

Cheers!

Three-dimensional structure of nitrate reductase: 
http://www.rcsb.org/pdb/explore/jmol.do?structureId=1q16&bionumber=&jmolMode=HTML5

 Program used to draw the cofactor: SketchEI

 Nitrogen metabolism figure: http://www.mdpi.com/2071-1050/3/9/1452/htm

 Fertilizer table: http://www.au.timacagro.com/products/plant-nutrition/root-and-foliar-biostimulants/fertileader.html

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