98 Otis F. Curtis 



Most manganese compounds are active oxygMi carriers or are easily 

 changed to such. This is especially true of potassium permanganate 

 and manganese dioxide. The latter, which is precipitated on and in 

 the twigs as just described, will almost instantly blue guaiacum or redden 

 aloin and decompose hydrogen peroxide. It can therefore act as an 

 oxidase, a peroxidase, or a catalase. Bunzell and Hasselbring (1917), as 

 stated above, have found that various organic compounds — glycerin, 

 tyrosine, ^ peptone, glucose, and others — will decompose potassium 

 permanganate, producing a precipitate of manganese dioxide and also 

 a solution containing some manganese which will give oxidase, peroxidase, 

 and catalase reactions. Whatever stimulation was obtained in these 

 experiments was probably due chiefly to this oxide adhering to the walls 

 or precipitated within the cells. It is probable that it was not due to 

 the permanganate itself, as this seemed very toxic to the roots of seedlings 

 or of herbaceous cuttings. In such cases the roots were formed when the 

 purple color was still present in solution. With the woody cuttings, how- 

 ever, all the purple color had disappeared before the roots started, and 

 the solution contained only the dark brown or black oxides of manganese. 

 In continuous treatments the solution may have contained also some 

 manganese available for oxidizing, as found by Bunzell and Hasselbring. 

 In those cases in which the treatment lasted for only a limited time, the 

 twigs were thoroly rinsed before being placed in the final medium, and 

 therefore no permanganate was carried over. 



It has been shown by several investigators that manganese is closely 

 associated with oxidation reactions occurring in plants. Bertrand (1897) 

 found it to be an important constituent of the oxidizing enzyme laccase. 

 When a sample of laccase was not very active, its activity was increased 

 by adding a small quantity of manganese sulfate. Schreiner, Sullivan, 

 and Reid (1910) found that the presence of manganese markedly increased 

 oxidation by soils and by plant roots. This occurs, however, only in 

 neutral or alkaline soils (Skinner and Reid, 1916). McHargue (1914) 

 found manganese to be especially abundant in the seed coats of various 

 seeds next to the cotyledons, and suggested that it played an important 

 r61e in respiratory activities during germination. He found that the 

 oxidase activity of different parts of seeds, tubers, roots, and stems varied 

 directly with the manganese content. Kastle (1910:122-131) cites sev- 



