364 Mineral Nutrition of Plants 



stem are so indicated and enclosed in parentheses; analyses of roots or 

 fruit are also placed in parentheses. 



Table I deals with the effects of nitrogen, phosphorus, and potassium 

 deficiency. The values for amino nitrogen in the leaves of nitrogen- 

 deficient plants seem to indicate a slight tendency to increase as com- 

 pared with the controls. If these ratios are averaged, however, it is seen 

 that the amino acid content of deficient plants is identical with that of 

 normal plants, while protein has decreased by one-third. On a relative 

 basis, however, ami no-nitrogen has increased as compared with protein. 

 Analogous values for the stems differ only slightly. Richards and 

 Templeman (j6) interpret their data on nitrogen deficiency to mean 

 that no marked disturbance of protein metabolism takes place. The 

 quantitative data tabulated for nitrogen deficiency verify the earlier 

 conclusions of Kraybill and Smith (2^) and Kraybill (22). An interest- 

 ing study of nitrogen deficiency in corn grown with ammonium-nitro- 

 gen (57) should be consulted. Wood and Petrie (6/) conclude from 

 their data that the concentration of sugar applied from an external 

 source did not disturb the relation of amino acids to protein in leaves 

 of Phalaris tuberosa L. Sucrose, glucose, and fructose were used. 



Results on phosphorus deficiency are less ambiguous. A definite in- 

 crease in amino acid nitrogen and decrease in protein is readily evident 

 both in the leaves and stems. This interpretation is supported by the 

 values of the means and again agrees with the interpretation of Richards 

 and Templeman (j6). The reasons for the apparent variations in the 

 results of different investigators are not entirely clear, except that those 

 data obtained with material from plants showing severe symptoms of 

 phosphorus deficiency show the greater differences. The phosphorus 

 deficiency data are also in accord with the prior work of Kraybill and 

 Smith (2j) and Kraybill (22) on tomato plants. Those of Turtschin 

 (55) and of Smirnov et al. {44) also show good agreement. 



Potassium deficiency studies seem to have been favored by investiga- 

 tors. These have reported, with few exceptions, that insufficiency of 

 potassium causes a disturbance in protein metabolism indicated by a 

 relative increase in amino acid nitrogen and a decrease in protein. Both 

 leaves and stems are affected. Richards and Templeman (j6) interpret 

 these results as due to breakdown of protein and not an inhibition of 



