EXPEEIMENT STATION EECOED. 129 



AGRICULTURAL BOTANY. 



Tlie function of manganese in plant growth, W. P. Kelley {Haivali Sta. 

 Bui. 26, pp. 7-//i). — A study has been niiide of the functiou of manganese in 

 plant growth, in which the author, after describing its occurrence in plants and 

 reviewing previous investigations, gives accounts of field and pot cultures with 

 different plants, the principal observations being made with pineapples. 



It was found that different species of plants vary decidedly when grown on 

 manganiferous soils. Some are stunted in growth and die back from the tips 

 of the leaves, while others api^ar unaffected and so far as can be determined 

 vegetate normally in the presence of manganese. Microscopic investigations 

 showed that certain changes take place in the protoplasm of the cells, the 

 chlorophyll in a number of plants being affected. In pineapples it imdergoes 

 complete decomposition, the chloroplasts often becoming disintegrated and 

 losing their granular structure. Simultaneously with the destruction of chlo- 

 rophyll starch formation ceases. The occurrence of oxidizing enzyms in plants 

 ai/liears to bear no direct relation to the destruction of chlorophyll under the 

 influence of excessive amounts of manganese, and there seems to be no corre- 

 lation between the phenomenon of chlorosis in pineapples and the activity of 

 the oxidizing enzyms. 



From ash analyses it was found that manganese was absorbed in consider- 

 able quantities, and. that the ratio of absorbed lime to magnesia increased 

 under the influence of manganese, regardless of whether the plant exhibited 

 any toxic effects. The author believes that the effects of manganese are largely 

 indirect and are to be explained on the basis of its bringing about a modifica- 

 tion in the osmotic absorption of lime and magnesia. The toxic effects are 

 chiefly due to this modification, rather than as a direct effect of the manganese 

 itself. 



Where small amounts of manganese occur in natural soils it is believed that 

 a twofold function in plant growth is performed. The manganese acts cata- 

 lytically, increasing the oxidations in the soil and accelerating the auto-oxida- 

 tions in plants, and it tends to modify the absorption of lime and magnesia by 

 partially replacing calcium from insoluble combinations and through a direct 

 effect on the osmotic absorption of lime and magnesia. 



The absorption of phosphoric acid by plants grown on manganiferous soil 

 was found to be decreased, possibly due to the precipifc^tion.by the manganese 

 of the phosphoric acid into a diflScultly soluble compound. 



The application of lime to manganiferous soils was found to result in a more 

 intense yellowing. On the other hand, the application of soluble phosphates 

 tends to ameliorate the effect of an excess of manganese. In practice this is 

 the only means known to be efficacious, but in the case of pineapples it does not 

 entirely prevent the development of the yellow color. 

 The form in which manganese is absorbed is not definitely known, but it is 

 suggested that it is probably as a manganite of calcium. 



The influence of manganese on the growth of Aspergillus niger, G. Beb- 

 TRAND and M. Javillier (Bui. Soc. Chim. France, 4- set:, 11 {1912), No. 5, pp. 

 212-221). — In continuation of previous investigations by the authors on the 

 effect of manganese, zinc, etc., on plants (E. S. R., 25, p. 325), a study is 

 reported on the action of manganese on the growth of A. ndger in cultures, 

 si)ecial efforts having been made to remove all traces of zinc, sulphur, etc., from 

 the manganese. Varying proportions of manganese were added to Raulin cul- 

 ture media and the effect on the growth of the fungus was observed. The 

 amount of manganese was varied from 1 part per million to 1 part in 50. In 

 all the experiments there was found a stimulating effect that rapidly increased 



