Lecture 4 — 101 — Movement and Distribution 



the relation between salt absorption and water absorp- 

 tion is not an indispensable one. The experiments on 

 barley plants as described earlier in this lecture afford 

 an illustrative case for the latter statement. 



In an active root system an upward moving salt 

 solution may be much more concentrated than the 

 dilute culture solution, if only a small amount of water 

 is being absorbed. When a large amount of water 

 is being absorbed the internal salt solution will under- 

 go more or less dilution. But in both cases metabolic 

 factors are involved. Due appreciation must be ac- 

 corded to movement of salt under the influence of 

 root pressure, under some conditions, especially in 

 young herbaceous plants. 



The emphasis I have given to the activities of living 

 cells is, I think needed, but this does not mean that 

 salt can not be absorbed and translocated through in- 

 jured or dead roots by a wick-like process. This is 

 an interesting point with reference to plants growing 

 in alkali soils in which some of the roots may become 

 injured by high salt concentrations or by alkalinity 

 and the factors associated therewith. 



Finally, I may remark that although our knowledge 

 of salt movement in the plant is still inadequate, 

 analysis of existing evidence may permit a closer 

 approximation to an understanding of these pheno- 

 mena than has been available in the past. Most im- 

 portant of all, it seems, is recognition of the fact that 

 the apparent simplicity of upward movement and 

 distribution of salt in plants may be illusory. In this 

 aspect of plant nutrition, it may be repeated, the 

 dynamic and integrated character of the whole system 

 is again emphasized. 



REFERENCES :- 



Arnon, D. I., Stout, P. R. and Sipos, F. Radioactive phos- 

 phorus as an indicator of phosphorus absorption of tomato 

 fruits at various stages of development. Amer. J. Bot. 27 : 

 791-798, 1940. 



