Oct. 1. 1920 Cause of Lime- Induced Chlorosis 37 



green plants from the two soils had almost equal percentages of lime and 

 potash in the ash, the percentage of total ash in the dry substance being 

 higher in the chlorotic plants. 



Numerous ash analyses were made at this Station from chlorotic and 

 green pineapple plants grown in soils with and without carbonate of 

 lime (12). Compared with the green plants, the chlorotic ones in the 

 calcareous soils contained more lime and less iron in the ash ; differences 

 in other ash constituents were slight or inconstant, potash as a rule being 

 fully as high in the chlorotic plants as in the green ones. 



Green and chlorotic rice plants were also analyzed at different ages for 

 their mineral constituents (13). In the case of rice grown 25 days, the 

 chlorotic plants from the calcareous soils contained much more lime, less 

 iron, and equal or greater percentages of potash in the ash than the green 

 plants from the soil containing no carbonate of lime; but in the case of 

 green and chlorotic rice of 84, 102, and 129 days' growth, the only con- 

 stant difference in the ash of the two kinds of plants was a greater per- 

 centage of lime in the chlorotic plants. These analyses and a special 

 study showed that the percentage of iron in the ash of rice diminished 

 very markedly as the plants became more mature (13). Since plants 

 affected with chlorosis matured much more slowly than normal plants, 

 probably the iron contents of the 84-, 102-, and 129-day samples were 

 affected more by the different maturities of the plants than by the char- 

 acter of the soils. 



Four pairs of samples of green and chlorotic sugar-cane leaves were 

 analyzed for their ash constituents. The leaves were selected from canes 

 which were of the same size and age and which were growing on the same 

 calcareous soil. In each case the chlorotic leaves had a distinctly lower 

 percentage of iron in the ash than the corresponding green leaves (19). 1 



A summary of the evidence from ash analyses in regard to the cause 

 of lime-induced chlorosis is as follows: Lime was determined in all seven 

 species of plants analyzed by the different investigators, and in five cases 

 it appeared that an excessive absorption of this element might be a cause 

 of chlorosis; in two cases it appeared that it was not. Potash was 

 determined in six of the different plants, and in only three cases did it 

 appear that a lack of potash might be a cause of chlorosis. Iron was 

 determined in five of the plants, and in all five cases it appeared that the 

 chlorosis might be due to a deficiency of this element. 



The weight of the evidence from the ash analyses seems to be that a 

 deficiency of iron in the ash is at least one cause of the chlorosis and that 

 possibly an excess of lime is also a cause. Against this conclusion there is 

 the opinion of many physiologists, as Euler (8), Jost (28), and Sorauer 



1 In a fifth comparison, leaves of green, slightly chlorotic, and chlorotic cane were analyzed, the canes 

 being of equal age but of markedly different size when grown on calcareous and noncalcareous soils. The 

 chlorotic leaves contained very slightly more iron than the green leaves. In this case, it is believed that 

 the maturities of the plants and the different ages of the leaves were the chief factors influencing the iron 

 content (19, p. is). 



