ZINK Ui'TAKE BV NEUROSPOKA 



913 



the weight of Nenrospora observed alter the lapse of 5 days (Table 1). 

 The capacity of the fungus to take up zinc was, however, not exhausted, 

 as shown by the fact that an eightfold increase in the zinc concentration 

 of the solution resulted in an almost threefold zinc uptake by the mould. 

 Feeney et al. (1947) determined the amount of zinc to be added to 



230- 



210 



190H 



° 170- 

 o 



a\50-\ 



130 



°^IIO 



5 90 

 ^ 70 



50 



30 



10 H 



~~i 1 1 1 1 — 



48 72 96 120 144 



Time ( hr.) 



168 



192 



Fig. 2. Dry weight of Neurospora without (Q) and after ( X ) addition 



of 30 figm. of zinc. 



the culture solution in order to obtain maximal growth and maximal 

 antibiotic formation in cultures of Bacillus subtilis. This was found to 

 be 0.40 mgm./L, while in the case of Neurospora crassa an almost maximal 

 growth was observed by us in the presence of as little as 0.08 mgm./l. 

 of zinc in the culture solution. 



Migration of zinc from the Neurospora into the cuUure solution 



By making use of isotopic indicators the migration of ions from the 

 plant into the culture solution has been observed in several cases, and 

 the effect on the migration process of unlabelled ions in the solution has 

 also been studied. Minute amounts of labelled lead, when taken up by 

 the roots of Vicia jaba, could to a large extent be removed by an excess 

 of non-labelled lead added to the nutrient solution, but to a minor extent 

 only if the solution did not contain lead (Hevesy, 1923). 



5 8 Hevesv 



