s 



1909] SCHREINER 6* REED— OXIDIZING POWER OF ROOTS 387 



expressing the relative oxidation shows, however, that the addition 

 of these salts produced relatively greater increases in oxidation than 

 in growth. When sodium nitrate was added to cumarin the resulting 

 growth w r as twice as great as where only cumarin was present; the 

 oxidizing power, however, was increased over fourfold. In com- 

 parison with this effect, it will be noted that the addition of sodium 

 nitrate to distilled water likewise increased the growth twofold and 

 increased the oxidizing powers two and a half times. It seems quite 

 evident, therefore, that the ameliorating powers observed under the 

 conditions of the experiment are to be referred to the increased 

 oxidizing powers w r hich are thereby brought about, and the consequent 

 diminution in amount and activity of the toxic material. 



It may be noted that Le Renard 39 found that nitrates had a 

 greater antitoxic value than other radicals when Penicillium was 

 grown in the presence of copper. 



SUMMARY 



1. Roots of growing plants exhibit an extracellular oxidizing 

 power which may be demonstrated by the use of suitable chromogens 

 in nutrient solutions or soil extracts. 



2. The oxidizing power appears to be most energetic in the region 

 of the root where root hairs are found, and to decrease gradually in 

 activity as that portion of the root becomes older. 



3. The oxidizing power of plants gnrwn in extracts of productive 



soils is greater than that of plants grown in extracts of unproductive 

 soils. 



4- Treating the soil extracts with an absorbing agent is usually 

 beneficial to oxidation. 



5- The distillate of a poor soil extract which contains volatile 

 to *ic compounds was less favorable to oxidation than the residue 

 remaining from distillation. 



6- The presence of toxic organic substances in solution was ex- 

 tremely deleterious to the oxidizing power of the plants. The oxi- 

 dizing power of the plants, especially in the presence of nitrates, 

 * as able to alleviate the toxicity of such solutions. 



39 Essai sur la valeur antitoxique de 1'aliment complet et incomplet. Paris. 1907. 



