MANGANESE AND THE GROWTH OF LEMNA

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Abstract
L. major had been shown by Clark and Fly to grow readily in inorganic salt solutions when no Mn could be detected by a method showing about 1 part of Mn in 800 million, and additions of that element did not increase rate of reproduction. By the use of the periodate oxidation in phosphoric acid, and by concentrating the solution, it was found possible to detect Mn in still smaller quantities, and by further purification to lower the content of the Mn in the medium. Lemna was grown free of micro-organisms under electric light, in 100 cc. of medium changed twice a week. At concentrations of Mn around 1:12,000-20,000 million no growth was obtained either with Fe supplied as chloride or as citrate. At concentrations around 1:3,000-4,000 million good growth occurred in both cases. With increased Mn the rate of reproduction rose, but soon reached a maximum, after which further additions had no effect on the rate of growth. Mn appeared to be essential in very small quantities.