Dec. 18,1916 
Assimilation of Iron by Rice 
527 
doubtless due to the reaction of the solution, calcium carbonate being 
present. In other solutions where ferric phosphate was the source of 
iron, addition of soluble phosphates produced chlorosis. The soluble 
phosphates here evidently precipitated the very small amount of iron that 
went into solution from the decomposition of ferric phosphate. Von 
Crone made the mistake of assuming that because ferric or ferrous phos¬ 
phate furnished sufficient iron in some solutions that it did in all solu¬ 
tions. Doubtless the reason that ferrous phosphate furnished sufficient 
iron in Von Crone’s solution was due to the fact that the concentration of 
phosphate ions was also particularly low. 1 
The results of this work, as well as that of Takeuchi (15) and Benecke 
(1), showed that soluble phosphates do not in themselves produce chlo¬ 
rosis. Benecke in his criticism of Von Crone’s solution failed to take 
into account that part of the iron he determined in his tests of the solu¬ 
bility of iron phosphates was colloidal iron. 
SUMMARY 
Rice was grown in acid, neutral, and alkaline solutions with different 
forms and quantities of iron to determine whether rice is particularly 
sensitive to the reaction of the solution and whether the reaction of the 
solution influences the assimilation of iron. 
In nearly all cases growth was much better in the nutrient solutions 
employed with 0.008 gm. of iron per liter than with 0.002 gm. When 
judged by the growth of plants ferrous sulphate, ferric citrate, and ferric 
tartrate afforded sufficient iron when used in proper quantities in the 
acid and neutral solutions. Ferric chlorid was an inferior source of 
iron, and dialyzed iron utterly inadequate. Only ferric tartrate fur¬ 
nished sufficient iron in the alkaline solution. 
Plants grown in the acid solutions contained the highest percentages 
of iron. Plants grown in the neutral solutions contained higher per¬ 
centages of iron than those grown in the alkaline solutions when some 
forms of iron were used, but equal percentages when other forms of iron 
were used. The percentages of nitrogen, phosphoric acid, lime, mag¬ 
nesia, and carbon-free ash in plants grown in six different solutions did 
not vary appreciably when compared with the iron content. 
It was evident that rice was not particularly sensitive to the reaction 
of the solution, except as the reaction influenced the availability of the 
iron. This substantiates previous work in showing that lime-induced 
chlorosis is caused by a lack of iron and indicates strongly that the only 
action of carbonate of lime in inducing chlorosis lies in diminishing the 
availability of the iron. 
The amount of available iron in the different solutions could not be 
determined analytically, because of the impossibility of distinguishing 
1 Ferrous and ferric phosphate evidently afford iron and phosphoric acid not through the dissolving action 
of plant roots, as Crone believed, but through the hydrolytic decomposition of these compounds. As a 
result of this decomposition, colloidal iron hydroxid is formed, as well as phosphate ions and a very small 
amount of soluble iron <9, 2). 
