190 



BIOCHEMICALLY IMPORTANT MINERAL ELEMENTS 



Courtesy of New Jersey Agricultural Experiment Station. Reproduced from 

 Hunger Sigtis in Crops, a publication of the American Society of Agronomy and 

 the National Fertilizer Association, Washington, D. C. 



Fig. 8-1. Right, manganese deficient leaves showing diminished chloro- 

 phyll content. Left, normal leaf. 





Courtesy of California Agricultural Experiment Station. Reproduced from 

 Hunger Signs in Crops, a publication of the American Society of Agronomy and 

 the National P^ertilizer Association, Washington, D. C. 



Fig. 8-2. Iron deficiency symptoms on lemon leaves. Left, normal leaf. 

 The other leaves show increasing lack of iron from left to right. 



sulinate is apparently not the active form of this hormone. A combina- 

 tion of zinc and protamine with insulin is widely used because it acts 

 much longer than insulin alone. 



Plants also require zinc. Fertile soils contain 1 to 5 parts per million 



