ABSTRACT
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In 1774, Scheele discovered manganese (Bryson et al., 2014). Since then, investigators interested in plant nutrition and in soil fertility have given considerable attention to the role of Mn in plant nutrition. McHargue (1922) is credited with showing that Mn is an essential element for plants. Arnon and Stout (1939) conrmed the essentiality of Mn in plant growth, according to the following criteria: the element is not considered essential unless (1) a deciency of it makes it impossible for the plant to complete the vegetative or the reproductive stage of its life cycle; (2) such deciency is specic to the element in question and can be prevented or corrected only by supplying this element; and (3) the element is directly involved in the nutrition of the plant, apart from its possible effects in correcting some unfavorable microbiological or chemical condition of the soil or other growth medium.
