674 



PLANT GROWTH AND PLANT COMMUNITIES 



TABLE I 



Transfer of Strontium from Strontium Membrane ( 195 ju, eq. Sr) 

 to H-Membrane via Solution and by Contact 



Transfer of Sr to 

 H-membrane 



Time 

 ( hours ) 



Via Solution By Contact Ratio, Contact 

 jU, eq/disc fx eq/disc to Solution 



24 



48 



172 



560 



1011 



2090 



00 (equilibrium) 



0.022 

 0.072 

 0.102 

 0.104 

 97.5 



50 

 82 

 90 



97.5 



4091 



1.0 



A strontium membrane was prepared by adding 195 fx eq. of 

 Sr(OH)2, tagged with Sr^^, to an H-membrane disc (diameter of 2.08 

 cm.) which was floating in 150 ml. of water. After a reaction time of 

 weeks the solution contained less than 0.54 /x eq. of strontium. Now a 

 second, equivalent, H-membrane was introduced into the same beaker, 

 such that it never touched the strontium partner. As anticipated, the 

 H-membrane sorbed the strontium in solution; new strontium moved 

 out of the strontium membrane and reacted with the second disc. 

 Vigorous agitation of the solution phase insured that diffusion of stron- 

 tium from one membrane to another through the centimeter-wide 

 water gap was not a rate-limiting step. According to Table I (Lopez- 

 Gonzales, 1959), transfer via the solution phase was exceedingly slow. 

 It would take many years to distribute strontium in equal amounts 



TABLE II 



Uptake of Sr by Plants Tied to a Sr-H-Membrane 

 (fjLg. of Sr per gram of oven-dry material) 



Plants in 

 Solution 



Plants in 

 Contact with 

 Sr-membrane 



Ratio, Contact 

 to Solution 



Leaves 

 Roots 



0.005 

 0.298 



0.023 

 0.641 



4.6 



2.2 



