CHAPTER 



\\J The Translocation of 

 Minerals in Plants* 



O. BIDDULPH 



I n multicellular organisms where one organ specializes 

 in mineral absorption, a distribution system for those minerals is an 

 inevitable development. The efficiency of the distribution system will, 

 in general, reflect the over-all efficiency of the organism since the 

 growth rate is dependent on an equalization of the necessities for 

 growth between the various organs and tissues. The growth rate may 

 not outstrip the supply of material upon which it is dependent. 



In plants there is no concentrated expenditure of energy for either 

 maintenance of body temperature or for muscular contractions, hence, 

 in keeping with the general level of specialization, there is no need for 

 a highly developed "circulatory system." Nevertheless, the transloca- 

 tion system must be efficient enough to distribute rapidly the incom- 

 ing materials, i.e., minerals, and to equalize concentrations between 

 various parts as tissue elaborations proceed. Even under the conditions 

 of reduced growth rates there is a continual exchange of materials 

 within the physical structure of the protoplasm which demands a con- 

 stant supply and removal of the basic components. The cellular entities, 

 such as the major morphological protoplasmic constituents, maintain 

 a relatively constant pattern even though the molecular or atomic con- 

 stituents undergo continual replacement. It is my purpose here to 

 review the translocation of minerals in plants with a view to correlat- 

 ing some of the observations on translocation with the requirements 

 of the organism. It will be necessary in many instances to resort to 



# The writer gratefully acknowledges the active participation of J. Witt, 

 J. Rediske, and C. Woodbridge in the research upon which parts of this report 

 are based. Figures i, 5 and 8, and 4 and 7 are from their respective theses in the 

 Department of Botany at the State College of Washington. 



