ASSIMILATION OF COLLOIDAL IRON BY RICE 



By P. L. GiLE, Chemist, and J. O. Carrero, Assistant Chemist, Porto Rico Agricul- 

 tural Experiment Station 



INTRODUCTION 



Previous work ' at the Porto Rico Agricultural Experiment Station has 

 shown that pineapples and upland rice grown on moderately or strongly 

 calcareous soils are affected with chlorosis and that the failure of these 

 plants to make a successful growth on such soils seems to be due wholly 

 or in part to a diminished assimilation of iron. A determination of the 

 forms of iron available to rice is therefore important. An experiment on 

 the assimilation of colloidal iron is reported here, as it bears on this prob- 

 lem as well as on the properties of plant roots. 



MATERIALS AND METHODS OF THE EXPERIMENT 



The availability of colloidal iron was compared with that of ferric 

 chlorid by growing upland rice in a nutrient solution. Water cultures 

 were used in this work, as it is impossible to tell in what form the iron 

 may be present in soil cultures. To prevent precipitation of the colloidal 

 iron by other salts of the nutrient solution the iron was put in one flask 

 (flask B) and the other salts in a second flask (flask A) . The plants were 

 grown with part of their roots in each flask. 



The seeds were germinated over distilled water until they had de- 

 veloped two or more roots. Two plants were grown in each pair of flasks. 

 Two hundred c. c. Erlenmeyer flasks of Jena glass with their necks 

 joined together by surgeon's tape were used. The formula for the 

 nutrient solution used in flasks A, which gave excellent results with rice 

 in previous work, was as follows: 



KNO3 o. 1017 gm. 



KH2PO4 0714 gra. 



NaNOs 2143 gm. 



NajSO, 0315 gm. 



CaClj o. 05 gm. 



MgCl., 05 gm. 



H.SO^ sec. N/io. 



Distilled water, 1,000 c. c. 



The plants were changed to fresh solutions every few days. 



The colloidal iron used was the ordinary dialyzed iron. It contained 

 0.0383 gm. of Fe and 0.0058 gm. of Clj per c. c. After salting out the 

 colloidal iron with potassium sulphate, the filtrate was examined and 

 found to contain the following, calculated as grams per c. c. of the original 

 dialyzed iron: Clj, 0.00436 gm. ; Fe, hardly a reaction with potassium 



• Gilc. P. L. Relation of calcareous soils to pineapple chlorosis. Porto Rico Agr. Exp. Sta. Bui. ir, 

 45 P-. 2 pl.. >9>'- 



Gilc, P. L.. and Ageton. C. N. The effect of strongly calcareous soils on tlie growth and ash composition 

 of certain plants. Porto Rico Agr. Kxp. Sta. Bui. 16, 45 p., 4 pi., 1914. 



Journal of ARricultural Research, Vol. III. No. 3 



Dept. of Agriculture, Washington, D. C. Dec. 15, 1914 



(205) B-3 



