75 LoHNis: Excess of Manganese 



Addendum:— Later experiments with lucerne showed that this plant also 

 is very susceptible to excess of manganese. The results will be published 

 in Plant and Soil, in the course of 1951. 



References 



1. Heintze, S. G., 1938: Journ. of Agric. Science 28:175. 



2. LoHNis, M. P., 1946: Tijdschr. over Plantenziekten 52:157. 



3. Steenbjerg, F., 1933: Tidsskr. for Planteavl 39:401. 



Points from Discussion of Pa^er hy Dr. Lohnis 



Prof. Steenhjerg:— 



Have you in Holland used a determination of the exchange- 

 able manganese of the soil with success as a criterion of manganese 

 deficiency disease? 



Dr. Lohnis:— 



It was outside the scope of this investigation but at an earlier 

 date^ I have tried whether the Asfergillus method might be made 

 suitable for the estimation of small amounts of manganese in soil. 

 It has appeared, however, that independently of the presence of 

 nitrate or ammonium salt as source of nitrogen, manganese de- 

 ficiency symptoms could merely be induced in very acid solution 

 (pH 2.5). In less acid solution Aspergillus developed abundantly 

 in the absence of any manganese intentionally added. So for 

 estimation of manganese in soil the method appeared of no use. 



Professor Wallace:— 



Regarding the point made by Dr. Lohnis that the injurious 

 effects of manganese toxicity of beans and non-injurious effects 

 on oats but injurious effects on the latter under conditions of de- 

 ficiency and that these may be related to ease of intake of manga- 

 nese: it should be noted that of the three plants quoted by Dr. 

 Lohnis, viz. French bean, strawberry and oat, in our experience 

 at Long Ashton French bean is highly susceptible to both manga- 

 nese toxicity and deficiency; strawberry is resistant to both; and oat 

 is resistant to excess but susceptible to deficiency. It would thus 

 not appear that a simple explanation based on ease of intake of 

 Mn accords with these observations. 



1 Antonie van Leeuwenhoek 10:101-122, 1944. 



