46 MINERAL SALTS ABSORPTION IN PLANTS 



constant in enzyme kinetics, { = ik^xk3)k^ when k^ is negligible), 

 and it is equal to the concentration of salt at which v reaches 50 per 

 cent of its maximum value. On plotting 1/v against \/s a straight 

 hne is obtained for which the ordinate intercept is \/V and the 

 slope =A's/K(cf. Fig. 8b). The apphcation of this treatment to salt 

 absorption data is discussed in more detail below (p. 58). It must be 

 emphasized that kinetic studies do not assist in distinguishing 

 between the various general mechanisms represented in Figs. 12 

 and 13, or in elucidating the chemical nature of the hypothetical 

 carriers. They do, however, supply evidence which is consistent 

 with the operation of a carrier system. 



For further reading 



Broyer, T. C. (1947). The movement of materials into plants. 11. The nature 



of solute movement into plants. Bot. Rev. 13, 125-67. 

 OvERSTREET, R. and Jacobson, L. (1952). Mechanisms of ion absorption by 



roots. Ann. Rev. Plant Physiol. 3, 189-206. 

 Robertson, R. N. (1958). The uptake of minerals. Encycl. Plant Physiol. IV. 



243-79. 

 Rosenberg, T. (1954). The concept and definition of active transport. Symp. 



Soc. Exp. Biol. 8, 27-41. 



