NITROGENOUS SOIL CONSTITUENTS 



59 



While xanthine has not been as thoroughly studied as the 

 hypoxanthine, in respect to its effect on plant growth, the results 

 obtained with this compound point, however, in the same direc- 

 tion, and sliow that xanthine is beneficial to plants. The effect 

 of xanthine in connection with fertilizer salts has not been studied 

 as the work was done earlier before the more extended method 

 with fertilizer salts was worked out. The xanthine is not very 

 soluble in water but a solution of 25 parts per million when 

 compared with a control culture in pure distilled water showed 

 an increase in green weight equal to 21 per cent, which is clearly 

 in harmony with the beneficial effects of hypoxanthine more 

 fully studied. 



GUANINE 



Guanine, the other common purine base resulting from the 

 breaking down of nucleo-proteins and nucleic acids, has also been 

 found in a soil.'' It is a constituent of guano and has been found 

 as a product of the autolysis of yeast. It appears to be rather 

 widely distributed and has been found in the seeds of vetch, 

 alfaKa, clover and gourd, in germinating barley, in sugar beet and 

 in sugar cane. 



Guanine, like xanthine, was tested in distilled water solutions 

 only, and ow^ng to its slight solubility a concentration greater 

 than 40 parts per million could not be tested. In this concen- 

 tration the increase in growth noticed was 5 per cent over that 

 of the growth in a distilled water control. The root development 

 was especially marked, long white and clear roots being obtained, 

 which were very healthy in appearance. The result indicates 

 that guanine should be classed as a beneficial compound. 



ADENINE 



Adenine has also been found as a soil constituent" and its 

 source in the soil is probably the same as those of the other 

 purine compounds, guanine, xanthine, hypoxanthine, already dis- 



«Schremer, 0. and Lathrop, E. C, Bull. 89, Bureau of Soils, U. S. Dept. of 

 Agric. 1912. 



' Shorey, E. C, Bull. 88, Bureau of Soils, U. S. Dept. of Agric. 1912. 



