Rothamsted Symposium on Trace Elements 64 



table, while the ripe, white seed, called "witte bonen," is dried and 

 used in the same way as brown beans. 



On the more acid plots, an injury to the foliage was noted 

 early in the summer of 1940; in all following years these symp- 

 toms occurred regularly in the same plots. In young leaves, a 

 strong marginal chlorosis, extending into the intervenal areas, oc- 

 curs. When older, the leaves become somewhat crinkled and 

 the intervenal areas show small whitish blotches. Finally, in the 

 latter, necrotic spots occur. Petioles and the lower parts of the 

 stem show small, brownish-purple spots. Severely injured plants 

 remain stunted and produce hardly any flowers or seed. Less in- 

 jured ones often recover, later in the season, but owing to the 

 initial injury the final yield is much smaller than usual. 



In the following years, a French dwarf bean, the variety 

 "Dubbele Prinsesseboon," was noted to be even more susceptible 

 to this injury. The chlorosis in the young leaves was most con- 

 spicuous and the canary-yellow plants may be recognized in the 

 fields from quite a distance. Purple spots on the petioles do not 

 occur. This variety has been studied most closely by us. 



Accidentally the cause of this injury became clear. In a 

 variety of beans ("van Tol's bruine boon") the occurrence of an 

 internal necrosis of the seed had been noted on certain soils. As 

 the phenomenon is very much like "marsh spot" in peas, caused 

 by a deficiency in manganese, I grew "van Tol's bruine boon" in 

 solution cultures, deficient in manganese, in order to ascertain 

 whether the injury might be induced by the same cause. In 

 order to learn also what symptoms would be induced in beans by 

 an excess of manganese, I prepared some cultures with large 

 amounts of MnS04. Quite unexpectedly, the symptoms induced 

 in this way appeared to be quite similar to those I had noted in 

 the fields. The same pattern of chlorosis, motding and crinkling 

 of the leaves occurred and the specific purple spots appeared on 

 the petioles. 



These observations induced us to compare the manganese con- 

 tent of healthy and affected foliage. In sampling healthy and 

 affected foliage always the youngest, full-grown leaves were 

 gathered. The air-dry material was analyzed for manganese 

 (method of Marshall as amended by Steenbjerg (3)). The 

 first analysis was made with material collected in 1943 from a num- 

 ber of varieties grown in the various fields. The affected leaves 

 contained much more manganese than the healthy foliage (2). 



