The 17 essential elements
Form used by plants:
Enzyme activator (decarboxylase, dehydrogenase, and oxidase enzymes)
Assists iron in chlorophyll formation
Assimilates CO2 in photosynthesis
Essential for phosphorus and magnesium uptake
Prominent in chloroplast membrane (structure containing the high absorbing chlorophyll pigment and C-assimilating mechanisms)
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.
Mobility in plant:
Not remobilized within plant
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:
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.
Excess iron, copper, or zinc may reduce Mn absorption.
Excess sodium or potassium may adversely affect Mn uptake.
Excess Mn encourages iron deficiency.
July 13, 2004