Robert A. Steinberg 383 



result of increased hydrolysis and not hindrance in synthesis of protein 

 is not supported by their data. Wall (59) discussed this point also and 

 disagreed with their interpretation particularly because of the presence 

 of ample sugar in the leaves to prevent hydrolysis. 



Another interesting comparison of these data is one based on the 

 hypothesis that mineral deficiency leads to a disproportionate content 

 of amino acids and reducing sugar as compared with normal plants. 

 Computation of the average deficiency-control ratios for all chemical 

 elements discloses that in 9 out of 10 instances amino nitrogen was 

 relatively greater than protein nitrogen in leaves, and only 4 out of 8 

 times in the stems. The analogous figures for reducing sugar and carbo- 

 hydrate were 5 out of 8 in leaves, and 3 out of 8 in the stems. Since 

 symptoms of abnormal nutrition are primarily localized in the leaves, 

 we may assume that mineral deficiencies lead to an accumulation of 

 amino acids as compared to protein, and of reducing sugar as com- 

 pared to carbohydrate. Extent and duration of deficiencies will probably 

 be found to cause progressive and opposite reactions in proportions of 

 carbohydrates. 



An accumulation of nitrate in deficient plants appears to be a general 

 phenomenon of mineral deficiency excepting nitrogen and boron. Since 

 deficiency symptoms appear in plants supplied with ammonium nitro- 

 gen, it must be assumed that inability to utilize nitrate is a result and 

 not a cause of symptoms. With the fungus, Aspergillus niger, only in 

 the case of molybdenum has a mineral deficiency been found dependent 

 on the source of nitrogen (45). Further studies with green plants will 

 presumably lead to similar results, inasmuch as Mulder (28) was able 

 to demonstrate a diminution effect of ammonium nitrogen on molyb- 

 denum deficiency in tomatoes, barley, and oats. 



In the tung and other trees, however, nitrate reduction apparently 

 occurs in the roots instead of the leaves, and no evidence has as yet 

 been found that mineral deficiency can cause an accumulation of 

 nitrate. Nitrates, it is known, can be caused to accumulate in leaves of 

 herbaceous plants by manipulation of climatic conditions irrespective 

 of mineral deficiencies. It is evident, therefore, that caution should be 

 exercised in attributing the accumulation of an intake material or 

 metabolite primarily to mineral nutrition. Such an accumulation may 



