55 Erkama: Copper, Manganese and Iron 



(12, 17). If we determine the copper and manganese content on 

 a protein basis, we find a negative correlation, in the tissue, be- 

 tween the protein content and manganese content. The copper 

 content, on the other hand, seems to be fairly constant. 



Iron in plant cells (1, 7, 9, 13, 15, 18, 19, 21, 23) occurs chiefly 

 in undissolved form. Most of it is bound in chloroplasts or in 

 the cytoplasm and mainly in the form of ferric iron. This "inac- 

 tive" or "residual" iron, is hardly dialyzable and seems to be in- 

 effective in chlorophyll production. On the other hand, the 

 fraction with a direct relation to chloroplasts, called "active" iron, 

 is more easily soluble in its ferrous form. According to Liebich 

 (15) 82% of the total iron in green spinach leaves is found in 

 chloroplasts, 5% in cytoplasm, and 13% in water solution. 



Table 12 : Sterile water culture experiments with peas: — 



Effect of Copper and Manganese on Iron Uptake:— In sterile 

 water culture experiments with peas, a synergism between the 

 copper and iron content of plants and an antagonism between 

 their manganese and iron content is obtained. The "A-Z solu- 

 tion" of HoAGLAND was uscd with the nitrate solution. In all 

 series iron was given in the form of ferric citrate. We will see 

 from Table 12 that the plants without copper nutrition contain 

 less iron per unit dry weight than the plants with copper. On the 

 other hand, the plants without manganese showed most iron. 



The effect of copper deficiency on the heavy metal content of 

 plants is shown very distincdy in an experiment where a pea plant 

 was grown from a copper-deficient seed in a culture solution with- 

 out copper. Seeds, deficient in copper, were obtained from plants 

 which had developed in a culture solution with a low copper con- 

 tent. Such copper-deficient seeds germinated so poorly that only 



