POTASSIUM 285 



biological material (K-9). The pattern of K^' uptake by sunflower plants 

 has been followed with a scintillation counter which permitted localization 

 of the activity in an area of 6.8-mm radius (K-10). The plants were 

 grown in vermiculite with No. 2 Iloagland's solution, to which the 

 K^-HCOs was added at the start of the experiment. For measurement, 

 the scintillation crystal was placed 1.6 mm above the leaf surface. 



K-l. Walker, W. Gordon, and Walter S. Wilde: Kinetics of Radiopotassiuin in 

 the Circulation, Am. J. PhijsioL, 170: 401-413 (1952). 



K-2. Hurst, W. U.: K"" Measurements in Body Fluids, ORNL-1165, Jan. 16, 1952. 



K-3. Johnston, Betty R., C. W. Duncan, Kirk Lawton, and E. J. Benne: Determina- 

 tion of Potassium in Plant Materials with a Flame Photometer, J. Assoc. Offic. 

 Agr. Chemists, 35: 813-816 (1952). 



K-4. Aikawa, Jerry K. : Effect of Starvation on Exchangeable Potassium and Tissue 

 K« Content in Rabbits, Proc. Soc. Exptl. Biol. Med., 78: 524-528 (1951). 



K-5. Greenberg, David M., Robert B. Aird, Muriel D. D. Boelter, W. Wesley 

 Campbell, Waldo E. Cohn, and Makio M. Murayama: A Study with Radio- 

 active Isotopes of the Permeability of the Blood-Cerebrospinal Fluid Barrier to 

 Ions, Am. J. Physiol., 140: 47-64 (1943). 



K-6. Love, William D., and George E. Burch: A Comparison of Potassium, Rubid- 

 ium, and Cesium as Tracers of Potassium in the Study of Cation Metabolism 

 of Human Erythrocytes In Vitro, J. Lab. Clin. Med., 41: 351-362 (1953). 



K-7. Mudge, Gilbert H.: Electrolyte Metabolism of Rabbit-kidney Slices: Studies 

 with Radioactive Potassium and Sodium, Am. J. Physiol., 173: 511-522 (1953). 



K-8. Krebs, H. A., L. V. Eggleston, and C. Terner: In Vitro Measurements of 

 the Turnover Rate of Potassium in Brain and Retina, Biochem. J. London, 48 : 

 530-537 (1951). 



K-9. Jacobson, Louis, Roy Overstreet, H. M. King, and Raymond Handley: A 

 Study of Potassium Absorption by Barley Roots, Plant Physiol., 26: 639-647 

 (1950). 

 K-10. Jonas, H.: The Time Course of K^^ Uptake by Sunflowers as Observed with a 

 Localizing Scintillation Count-rate Meter (In press). 



