Lecture 2 



41 — 



Micronutrient Elements 



The experimental plant was again that guinea pig of 

 the plant physiologist — the tomato. Clearly not much 

 can be learned about the function in a plant of a 

 nutrient element if the deficiency is so acute that the 

 plant makes almost no development. In these experi- 

 ments the supply of zinc was so regulated for some 

 sets of plants that the plants attained only an in- 

 cipient state of zinc deficiency; that is, there was no 



22. 2t 



Days In Cultvre. 



Protein nitrogen In leaf blades of Experi- 

 ment B, calculated as the difference between 

 total nitrogen and total soluble nitrogen. 

 • Hlgh-zlnc series. Low-zinc series. 

 O Recovery series* 



Textfigure 7, — Protein nitrogen in leaf 

 blades of tomato plants as influenced by ap- 

 plication of zinc during growth, showing re- 

 sponse in protein synthesis in zinc deficient 

 plants after adding zinc. The deficient plants 

 were in only an incipient state of zinc defi- 

 ciency. (From R. S. Bean, 1942). 



observable symptom of deficiency within the time 

 period allowed, although it was known that zinc de- 

 ficiency symptoms would appear later. Other sets of 

 plants had a larger supply of zinc, suflficient to protect 

 them against zinc deficiency for a long period. At 



