3 8o 



Mineral Nutrition of Plants 



Figure 3. Maryland Medium Broadleaf tobacco in asceptic culture il- 

 lustrating the effect of 200 p. p.m. of synthetic isoleucine. 



nitrogen, 32; phosphorus, 48; potassium, 587; calcium, 120; magnesium, 

 283; boron, 27; and frenching, 94. Chloroses were attributed primarily 

 to the accumulation of toxic metabolic products and were not, except 

 possibly magnesium, evidence of a function in chlorophyll formation. 

 An important corollary of these results has a direct bearing on the 



