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The 17 essential elements
are:
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Manganese (Mn)
Form used by plants:
Mn2+
Important functions:
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Enzyme activator (decarboxylase, dehydrogenase, and oxidase enzymes)
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Assists iron in chlorophyll formation
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Assimilates CO2 in photosynthesis
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Essential for phosphorus and magnesium uptake
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Prominent in chloroplast membrane (structure containing the high absorbing chlorophyll pigment and C-assimilating mechanisms)
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Important in N metabolism and assimilation
Ideal foliage range for apple leaves:
25-100 ppm leaf dry weight
Ideal fruit concentration:
Ideal soil range:
> 1.5 ppm
Deficiencies are most common on soils with pH . 7.0. Toxicities may occur on acid soils.
Mn is relatively not mobile in soils.
Best indicators:
Mobility in plant:
Not remobilized within plant
Deficiency symptoms:
Vegetation symptoms: interveinal chlorosis developing in older leaves first. In severe cases, heavy defoliation may occur. Rust spots or a mottled pattern may be an indication on some plants.
Increased risk of Mn deficiencies:
Availability of Mn decreases as pH increases (at soil pH 6.3, Mn becomes insoluble)
Excess problems/Interactions with other elements:
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In acid soils, toxicity may occur especially on Delicious and Jonathan apples. Signs may include chlorosis, early leaf abscission, reduced flower bud development, and internal bark necrosis.
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Excess iron, copper, or zinc may reduce Mn absorption.
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Excess sodium or potassium may adversely affect Mn uptake.
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Excess Mn encourages iron deficiency.
Updated
July 13, 2004
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