Rothamsted Symposium on Trace Elements 54 



Some Aspects of the Occurrence of Copper, Manganese, 

 and Iron in Plants:— It is clear from analytical data that external 

 factors have more eflfect on the manganese content of a plant than 

 on its copper or iron content. The manganese content of plants 

 also varies more than that of the other heavy metals. This is 

 shown in Table 10 which gives a survey of variations in copper, 

 iron, and manganese content of a number of plant samples. 



If we compare the copper, iron, and manganese content of ash 

 with the ash content of a plant, we see that the uptake of heavy 

 metals is apparently the reverse of the uptake of other ash com- 



Table 11: Relation of the ash content of plant to the 

 heavy metal content of ash in some plant leaves: — 



ponents. The copper or iron content of ash seems to be fairly 

 independent of the relative ash content of plants. Between the 

 manganese content of ash and the ash content of plants there 

 exists, on the other hand, a distinct negative correlation, as we will 

 see from Table 11. Most of the plants analyzed there had been 

 grown in the same soil. The ratio Cu:Fe seems to be more con- 

 stant than the ratio Mn:Fe. The smaller the ash content of a 

 plant, we note, the more manganese it contains. 



Copper has been found strongly bound in protoplasm. Man- 

 ganese, on the contrary, seems to be easy to dialyze from the cell 



