NITROGENOUS SOIL CONSTITUENTS 



51 



parts per million of nitrate, just discussed. This is shown by 

 the results in Table III. The total green weight of the cultures 

 without the nucleic acid was 26.483 grams, against 29.730 grams 

 for the nucleic acid cultures, an increase of 12 per cent. 



In the cultures of higher nitrate content the effect of the nucleic 

 acid was not more noticeable than that already noted in the 

 case of the cultures with 16 parts per million of NH3 as nitrate. 

 The series of cultures containing 24 parts per million of NH3 

 as nitrate showed an increase of 11 per cent on the addition of 

 nucleic acid; the 32 parts per milUon series showed an increase 

 of 13 per cent; the 40 parts per million, 14 per cent; the 48 parts 

 per miUion 15 per cent; the 56 parts per million 7 per cent; the 

 64 parts per million, 20 per cent; the 72 parts per million, 10 

 per cent; the 80 parts per milUon, no increase. 



Absorption of nitrate in the presence of nucleic acid 



It is apparent from the foregoing that nucleic acid is beneficial 

 to growth and that its effect is most marked in nitrate free solu- 

 tions, showing that it can take the place of nitrates in producing 

 growth. With increasing nitrate content the effect of nucleic acid 

 in increasing growth, beyond that produced by the nutrient salts 

 becomes less, but is nevertheless appreciable. That it still plaj-s 

 a part in taking the place of nitrate in producing growth, even 

 in the solutions which contain nitrate, is shown by the result in 

 anal3'tically determining the removal of nitrate from the culture 

 solutions during growth. The culture solutions were changed 

 every three daj^s, as already mentioned, and the amount of 

 nitrate remaining in the solution determined. In this way it 

 was found that in the cultures containing no nucleic acid the 

 totar quantity of nitrate removed was 666.8 mgms., whereas the 

 amount of nitrate removed in the presence of nucleic acid was 

 orAy 516.1 mgms, thus showing a greatly diminished nitrate 

 requirement, when nucleic acid is furnished the plant, although 

 a much greater growth has resulted. 



The culture work ^v•as throughout under strict chemical con- 

 trol, so as to' estabHsh as definitely as possible that the effects 



