MANGANESE CHLOROSIS OF PINEAPPLE. 3 
in the bleaching out of the chlorophyll. The juices of such plants 
show more intense reactions for oxidase and peroxidase than the 
healthy control plants." 
Aso (1) in similar water cultures with young radish, barley, and 
wheat plants observed a yellowing with solutions containing (a) 0.02 
percent MnS0 4 + trace of FeS0 4 , (b) 0.02 per cent MnSO 4 + 0.02 
per cent FeS0 4 in comparison with (c) 0.02 per cent FeS0 4 and in 
these three solutions diluted with 10 times their volume of water. 
The ordinary mineral constituents were supplied. When the solu- 
tion containing manganese sulphate and only a trace of ferrous sul- 
phate was diluted 10 times the yellowing suggested a lack of iron. 
JPea shoots grown during the first stage of development in solutions 
containing no mineral salts and only 0.002 per cent ferrous sulphate 
and manganous sulphate singly and in combination found the great- 
est stimulation with the manganous sulphate. No yellowing was 
observed during this first stage of development. Aso concludes that: 
(1) Manganese salts exert on the one hand an injurious action and on the 
other a stimulant influence on plants; with increased dilution the former dimin- 
ishes while the latter increases. Thus a dilution can be reached in which only 
the favorable action of manganese becomes obvious. 
(2) Manganous sulphate added in a dilution of 0.002 per cent to culture solu- 
tions exerted a stimulant action upon radish, barley, wheat, and pea. Iron 
seems to counteract to a certain degree the action of the manganese. 
(3) The intensity of the color reactions of the oxidizing enzyms of the man- 
ganese plants exceeds that of the control plants. 
That the injurious effects of manganese may be due to a depressed 
assimilation of iron does not appear to be suspected in the later work 
of Aso (2, 3) and other investigators. 
Katayama (27) found an increase in yield of barley when small 
amounts of manganous sulphate were used. Large amounts of man- 
ganese retarded growth. 
In 1907 Salomone (39) published the results of an extensive inves- 
tigation with various salts and oxids of manganese. A slight yellow- 
ing was observed in wheat in field experiments when small quantities 
of the oxids were used, but the final yield was increased. Serious 
injury was observed when manganese as manganous sulphate was 
applied at a rate greater than 50 kilograms per hectare, and the 
plants died when still larger quantities were used. The toxic effects, 
due to manganese, seem to be similar to those which the pineapple 
plant suffers on manganiferous soil, i. e., a yellowing, disorganization 
of the chlorophyll bodies, and other physiological derangements. 
The crop was injured also when these plats were planted to wheat 
for the second time. It is significant that lime and basic slag appli- 
cations did not diminish this toxic effect as was also the case in the 
liming experiments on the manganiferous soils of Oahu. 
Salomone also found that fcpavy applications of various manganese 
compounds caused the death of bean plants which were grown in 
boxes and that the toxicity of manganese was greater where manga- 
nese functioned as an electronegative element. 
Hall (21) thinks that in field experiments the stimulating action of 
manganese is due to some indirect effect on the dormant bases of the 
soil rather than to a direct effect of the manganese. He does not, 
however, consider this point established. 
