10 BULLETIN 42, U. S. DEPARTMENT OF AGRICULTURE. 



Loew and Sawa 1 grew barley plants in a 0.1 per cent MnS0 4 solution. 

 An injurious action was observed in. this dilution, and after several 

 days a change in color from green to yellow was evident. The reac- 

 tions for the oxidizing enzymes were more intense with the manga- 

 nese plants than the control plants, which accounts for the fading 

 or bleaching out of the chlorophyl. In discussing the stimulation 

 by manganese Loew suggests that manganese increases the oxidiz- 

 ing power of oxidizing enzymes, and thus aids in destroying injurious 

 compounds as fast as they are formed, or checking their formation. 



Brenchley 2 made some water culture experiments with manganese 

 sulphate. In solution of 100 parts per million barley was injured, 

 the roots turned dark, and the leaves appeared diseased. Even 

 with 10 parts per million the barley was injured, but not so badly as 

 in the stronger solution. Concentrations less than 1 part per million 

 caused stimulation. Manganese was found in the leaves of the 

 plant. 



Voelcker 3 working with wheat in water cultures found that manga- 

 nese iodide produced a thin delicate root development, a peculiarity 

 which was accentuated in a stronger solution. Manganese dioxide 

 gave a good growth, with a wealth of finely branched roots which 

 were not noticed in the untreated. 



Schreiner, Sullivan, and Reid 4 have shown that the oxidation of 

 soils was increased by the addition of manganese, that soils, though 

 having similar amounts of manganese, varied greatly in oxidizing 

 power, and that oxidation in soils depended on the form of the man- 

 ganese as well as the amount. The form of the organic matter of 

 the soil also controls the oxidizing power. The oxidative power of 

 the manganese salts was increased by some organic acids and de- 

 creased by others. 



Schreiner and Reed 5 studied the oxidizing power of plants growing 

 in soil solutions. They found that the oxidizing power of the plant 

 was greater in extracts of productive soils than in extracts of unpro- 

 ductive soils. In one experiment the oxidizing power of plants 

 growing in distilled water was compared with that in an extract of a 

 poor soil and of a good soil. Putting the distilled water at 100, the 

 relative oxidation in the poor soil extract was 72 and in the good soil 

 extract 286. In another experiment a poor sandy loam was com- 

 pared with a rich garden soil. When the oxidation of the plants in 



i Loew, O., and Sawa, S., On the action of manganese compounds on plants. Bui. Col. Agr., Tokyo, 

 6, 161 (1902-3). 



2 Brenchley, The influence of copper sulphate and manganese sulphate upon the growth of barley. Ann. 

 Bot., 24, 571 (1910). 



3 J. Royal Agr. Soc. Eng., 65, 313. 



< Schreiner, O., Sullivan, M. X., and Reid, F. R., Studies in soil oxidation. Bui. 73, Bureau of Soils, 

 U. S. Dept. Agr. (1910). 



' Schreiner, O., and Reed, H. S., The role of oxidation in soil fertility. Bui. 56, Bureau of Soils, U. S. 

 Dept. Agr. (1909). 



