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PLANT ROOT-SOIL INTERACTIONS* 



Hans Jenny 



UNIVERSITY OF CALIFORNIA, BERKELEY 



The boundary phenomena of root and soil include observations of long 

 standing. Designating a root as \ / , the opposing processes in the 

 boundary region may be represented schematically as follows : 



Soil 



entries (influx) 



exits (outflux) 



Non-living matter that enters the root may in part be arranged as 

 follows : ( 1 ) Water-flow from the soil into the root as a consequence of 

 transpiration pull and diflFusion gradients ( Bonner, 1959; Bernstein et 

 al., 1959). (2) Entry of dissolved substances with the transpiration 

 stream ( Hylmo, 1958 ) and by diffusion ( Hope and Stevens, 1952; Rob- 

 ertson, 1956, 1958). These may be subdivided as (a) gases, especially 

 oxygen and carbon dioxide; ( b ) mineral nutrients, mainly as inorganic 

 ions; and (c) organic molecules (and ions) of low and high molecular 

 weight— as high as 63,000, represented by hemoglobin (Jensen and 

 McLaren, 1960 ) . It is well established that the mineral influx is to some 



" This ivork luas in part supported by Atomic Energy Commission Contract 

 AT(ll-l)-34. 



665 



