81 Burstrom: Manganese and Roots 



and nitrate on excised roots. One experiment, continued for 

 three days, gave the following result: — 



Without nitrate the cells and the roots become disorganised and 

 the figures are of litde interest. But also, with the treatment 

 without manganese cell elongation declined; it continued normally 

 only in the presence of both nutrients. Nitrate, indeed, shows its 

 full action only in the presence of manganese. 



I do not know if manganese is indispensable for the continued 

 growth of excised wheat roots. Glasstone (Am. J. Bot. 1947) 

 has recently stated that tomato roots only need Fe and Cu but not 

 Mn. We have not investigated this problem, in particular, in 

 tests of long duration, but I am inclined to believe that roots need 

 manganese for normal growth. 



Another point that has not been clarified is the interaction of 

 iron and manganese with respect to the properties of the roots 

 which we studied. Preliminary experiments have shown, how- 

 ever, that the manganese action occurs, both in the absence and 

 the presence of iron, if given in the same concentration in both 

 cases. Iron itself causes, in the absence of manganese, a marked 

 reduction in the length of cells, apparently owing to a more rapid 

 cell development. This action seems to be weakened if manganese 

 is present, as shown by an example: — 



It is obvious that manganese and iron do not have altogether 

 contrary actions on the cell growth, which they should have, if 

 the opinion of Shive as to the interaction of iron and manganese is 

 generally valid. 



