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  Section: Plant Nutrition » Micronutrients » Manganese
 
 
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Forms of Manganese and Abundance in Soils

 
     
 
Content
Introduction
Forms of Manganese and Abundance in Soils
Importance to Plants and Animals
  Essentiality of Manganese to Higher Plants
  Function in Plants
  Importance to Animals
Absorption and Mobility
  Absorption Mechanisms
  Distribution and Mobility of Manganese in Plants
Manganese Deficiency
  Prevalence
  Indicator Plants
  Symptoms
  Tolerance
Toxicity
  Prevalence
  Indicator Plants
  Symptoms
  Tolerance
Manganese and Diseases
Conclusion
References

Manganese is the tenth-most abundant element on the surface of the earth. This metal does not occur naturally in isolation, but is found in combination with other elements to give many common minerals. The principal ore is pyrolusite (MnO2), but lower oxides (Mn2O3, Mn3O4) and the carbonate are also known.

Manganese is most abundant in soils developed from rocks rich in iron owing to its association with this element (1). It exists in soil solution as either the exchangeable ion Mn2+ or Mn3+. Organic chelates derived from microbial activity, degradation of soil organic matter, plant residues, and root exudates can form metal complexes with micronutrient cations, and thereby increase manganese cation solubility and mobility (2). Availability of manganese for plant uptake is affected by soil pH; it decreases as the pH increases. Divalent manganese is the form of manganese absorbed at the root surface cell membrane. As soil pH decreases, the proportion of exchangeable Mn2+ increases dramatically (3), and the proportions of manganese oxides and manganese bound to iron and manganese oxides decrease (4). This action has been attributed to the increase in protons in the soil solution (5). Acidification may also inhibit microbial oxidation that is responsible for immobilization of manganese. Manganese-oxidizing microbes are the most effective biological system oxidizing Mn2+ in neutral and slightly alkaline soils (6–8). Relatively, as soil pH increases, chemical immobilization of Mn2+ increases (9), and chemical auto-oxidation predominates at pH above 8.5 to 9.0 (10,11).


 
     
 
 
     



     
 
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