244 G. E. Blackman 



the end of 32 hrs. bears little relationship to the pattern of uptake. 

 For example, the proportion of the total amount absorbed transferred 

 to the shoots of the five resistant species (Figures 1 and 2) varied from 

 3.8 per cent (Triticum) to 10.9 per cent (Oryza), while the correspond- 

 ing figures for the susceptible species ranged from 1.2 per cent (Helian- 

 t lilts) to 25.0 per cent (Brassica). However, on the basis of preliminary 

 experiments on the uptake of 2,4-D by susceptible and resistant inbred 

 lines of Zea, it would appear that between inbred lines the pathways 

 or mechanisms operating in the transport of 2,4-D out of the leaf 

 may be different, while those controlling the uptake and movement 

 from the roots through the endodermis into the transportation stream 

 are similar. 



Woodford et al. (9), in their review, have emphasized that 2,4-D 

 can affect a wide range of enzyme systems and cellular processes, but 

 that no individual effect can satisfactorily account for selective action 

 at cell level. It is more reasonable to suppose that selective action rests 

 on the extent to which the auxin interferes with the organized pat- 

 tern of cell growth and differentiation. Such a general interference 

 could be brought about by changes in the physical and chemical 

 properties of the interfaces or barriers within the individual cells. 

 The present investigation has demonstrated that the complex of fac- 

 tors which are grouped under the aegis of permeability alloA\s the 

 movement of 2,4-D out of one species more than another. Previous 

 research (I, 3) has shown that 2,4-D and TIB A respectively can reorien- 

 tate the course of uptake of, for example, potassium and cerium- 144. 

 Similarly, Sacher and Glasziou (6) have found that indole-3-acetic acid 

 (lAA) and 1-naphthaleneacetic acid inhibit both the injection of the 

 intercellular spaces with water and the exudation of sugars and salts 

 by segments of deseeded bean pods at a time when the cells are still 

 capable of being plasmolyzed and deplasmolyzed. It would seem that, 

 if the auxin which is introduced persists in the tissues, then on the 

 basis of information theory only very small changes between or within 

 cells are demanded to bring about ordered or disordered celhdar 

 development. 



ACKNOWLEDGMENT 



Many of the results reported in this paper have been obtained by 

 E. Abeyaratne during his research for a higher degree at Oxford. 



LITERATURE CITED 



1. Bliickman, G. E. Interrelationships between tlie uptake of 2:4-dicliIoi(>phcnoxy- 

 acciic acid, growth, and ion absorption. Iti: R. L. ^Vain and F. Wightnian (eds.) 

 The Chemistry and Mode of Action of Plant Growth Substances, pp. 253-259. 

 Butterworth Sci. Pub!., London. 1956. 



