IMPORTANCE OF MANGANESE

INTRODUCTION

Plants quantitative and qualitative yield is strongly dependent on plant nutrition.In addition,in plant nutrition each element should be available in adequate amount for plant,also balance and respect ratio between used nutrient is important.Manganese(Mn) place an important role in oxidation and reduction processes in plants,such as the electron transport in photosynthesis.Manganese also has played a role in chlorophyll production,and its presence is essential in photosystem II.

The importance of manganese are thus highlighted as:

Manganese act as an activating factor which causes the activation more than 35 different enzymes.Due to the metabolic role of manganese in the nitrate-reducing enzyme activity and activation of enzymes which play roles on carbohydrates metabolism,use of fertilizer containing manganese increases efficiency of photosynthesis and carbohydrates synthesis such as starch,thus photosynthesis efficiency decreases with manganese deficiency and therefore crop yield and quality will be reduced.

Manganese is uptake and transfers the form of Mn2+ in plants,and transfers the meristematic tissue gradual,thus the young organ of plants are rich in manganese.Calcareous soils i.e soil with high pH(mainly in arid and semi-arid areas of the world)and especially in cells with poor ventilation are confronted with manganese deficiency. Magnesium(Mg) and lime have an antagonistic effect on manganese,therefore manganese uptake decreases by magnesium and lime.

Plant nutrition is one of the important problems in crop production which have an important role in crop production and improve agricultural production quality.In most regions of the world,the use of chemical fertilizer is very unbalanced and is not based on plant requirement.Each element in proper plant nutrition should be available enough for plant,and balance and respect the ratio between used nutrient is also important.

Manganese is one of the main micro nutrients,which has an important role in plants as a component of enzymes involved in photosynthesis and other processes.Manganese is part of an important anti-oxidants (superoxide dismutase) structure that protect plant cells by de-activating free radicals which can destroy plant tissue.

MANGANESE DEFICIENCY IN PLANTS
Manganese deficiency is a widespread problem,most often occurring in sandy soils,organic soils,with a pH above 6 and heavily weathered,tropical soils.It is typical worsened by cool and wet conditions.Numerous crop species have been reported to show high susceptibility to Mn deficiency in soils,or a very positive response to Mn ferterlization,including cereal crops(wheat,barley and oats),legumes(common beans,peas and soya bean),stone fruits(apple,cherries and peaches,palm crops,citrus,potatoes,sugar beats and canola among others.

The impact of Mn deficiencies on this crops includes:

Reduced dry matter production and yield,weaker structural resistance against pathogens and reduced tolerance to drought and heat stress.

Manganese has a relatively low phloem mobility in plants and as a result,typical leaf symptoms of Mn deficiency first develop in younger leaves. The critical concentration fro Mn deficiency is generally below 20 ppm dry weight in fully expanded,young leaves.

In case of dicot, Mn deficiency forms result in pale mottled leaves,followed by typical inter-venial chlorosis.Under severe Mn deficiency dicot may also develop a number of brownish spot.

In cereals,Mn can cause pale green or yellow patches in younger leaves.This condition is known as grey speck,and is characterised by necrotic spots that form in older leaves.