37° Mineral Nutrition of Plants 



parallelism between severity in symptoms and degree of chemical change 

 has been noted for boron by Steinberg, Bowling, and McMurtrey (50). 

 A microchemical study by Wadleigh and Shive (5$) led these investiga- 

 tors to conclude that boron deficiency caused an alteration in the 

 normal course of protein synthesis in cotton seedlings. 



EFFECTS OF MINERAL DEFICIENCIES ON THE REDUCING SUGAR 

 AND CARBOHYDRATE CONTENT OF PLANTS 



Nitrogen, phosphorus, and potassium deficiencies in Table IV also 

 reflect the effects of divergencies in sampling and climatic conditions. 

 However, certain variations in composition have been noted by in- 

 vestigators in their experiments. These changes consist, with nitrogen 

 deficiency, of a relative decrease in reducing sugar and an increase in 

 total carbohydrate. The increase in carbohydrate is attributed to dimi- 

 nished formation of protein. Phosphorus deficiency leads to equal in- 

 creases in both fractions for the same reason, while lack of potassium 

 causes a greater increase in reducing sugar than in total carbohydrate. 



The mean values for nitrogen deficiency in Table IV indicate a 

 relative decrease in reducing sugar as compared with total carbohydrate 

 both in leaves and stems. Reducing sugar apparently increased rela- 

 tively to carbohydrate only in the stems of plants subject to phosphorus 

 deficiency, but not in the leaves. MacGillivray's data (Table VII) would 

 indicate this to be only an apparent exception. With potassium defi- 

 ciency, reducing sugars again seemed to show a relative increase as 

 compared with carbohydrate in both stems and leaves on the basis of 

 the mean values. 



Analytical data on the contents of reducing sugar and carbohydrate 

 are very limited in the cases of magnesium, calcium, and sulfur defi- 

 ciencies. Table V presents the available data. Almost invariably there is 

 a decrease in both fractions in both leaves and stems with these three 

 elements. Only in the case of stems short of calcium is there a slight 

 increase in both reducing sugar and total carbohydrate. 



Micronutrient deficiency effects on reducing sugar and carbohydrate 

 have been tabulated in Table VI. Iron-deficient pineapple plants are 

 lower in total carbohydrates than are the controls and this is accom- 

 panied by a slight relative increase in reducing sugar. Both leaves and 



