406 



8. INHIBITOR DISTRIBUTION IN LIVING ORGANISMS 



of inhibitors in plant tissues but recently much work has been done on the 

 movements and distribution of herbicides, such as 2,4-dichlorophenoxy- 

 acetate (2,4-D), in the higher plants, and the results probably are often 

 applicable to the more common enzyme inhibitors when they are applied to 



— 200 



MAO INHIBITION 



LIVER IPRONIAZIO 



00 



50 



TIME (HOURS)- 



200 



250 



Fig. 8-2. Tissue concentration of iproniazid and the inhibition of monoamine oxi- 

 dase following intraperitoneal injection of 195 mg/kg in rats. The curves are for the 

 liver but brain and muscle are similar. Curve 1: tissue concentration (//g/gm); curve 2: 

 monoamine oxidase inhibition (MAO). (From Hess et al., 1958.) 



plants in the same ways as the herbicides. The distribution, as in animals, 

 depends on the manner of administration, the absorption through certain 

 tissues, and the circulation within the plant. 



Route of Administration of the Inhibitor 



There are two general ways in which inhibitors may be applied to intact 

 plants: in the soil or solution for uptake by the roots or on the upper leafy 

 parts of the plant. In either case the inhibitor may spread through the cir- 

 culatory pathways from the site of absorption. The factors involved in pene- 

 tration into the roots are little known but the process may well be complex 

 since active transport for ions is well established and the flow rate of 

 water is often dependent on transijiration conditions in the leaves. Inasmuch 

 as absorption into the roots depends on metabolic energy, an inhibitor can 



