Source. Like iron, the oxide forms of manganese are common in soil. However, manganese dioxide (highly oxidized form) is not easily available to plants. Increased acidity leads to increase in solubility of manganese. In strong acidic soils, manganese may be present in toxic concentrations. Oxidizing bacteria in soils render manganese unavailable to plants at pH ranging from 6.5 to 7.8.

Regions. Manganese is required in leaves and seeds.

Functions. It activates enzymes like carboxylases, oxidases, dehydrogenases, peroxidases and kinases. It is required for the formation of pigment chlorophyll. It decreases the solubility of iron by oxidation. Hence, abundance of manganese can lead to iron deficiency in plants.

Deficiency symptoms

(i) Chlorosis (interveinal)
(ii) Chloroplasts lose chlorophyll, turn yellow green, vacuolated and finally perish.
(iii) Occurrence of grey spots on leaves.
(iv) The root system is often poorly developed.
(v) Grey spot disease in oat appears due to the deficiency of manganese, which leads to total failure of crop.