Improvement of Groioth Regulalor I-'oi innldtion 



797 



Amitrol after entering the phloem has moved to root and shoot 

 tips; its movement has been limited to phloem. Under like condi- 

 tions MH has moved throughout the phloem; it also has transferred 

 to xylem and entered every transpiring leaf. This compound, like 

 phosphorus, is evidently able to circulate in the plant. Dalapon seems 

 to resemble MH in this respect. 



Keeping these various responses in mind it is interesting to exa- 

 mine the constituents of a spray formulation and seek out their var- 

 ious functions. The surfactant plays several roles: it promotes wetting 

 of the cuticle and hence may bring about stomatal uptake when 

 stomata are open. The surfactant may serve as a filming agent and 

 cosolvent holding the regulator molecules in a liquid layer in inti- 

 mate contact with the cuticle when the water in the spray has evapo- 

 rated. And if the surfactant dries to a liquid film of low surface ten- 

 sion and highly lipophilic properties it may creep along the surface 

 of the cuticle, pass the entrapped bubbles in the micro-capillaries, 

 and make contact with the water continuum. These various func- 



\ I 



1 



2^4,0 



lAA 



Amitrol 



Fig. 6. Comparative mobility of 2,4-D, lAA, and amitrol in barley. Pair of plants 

 on left in each group treated on leaf no. 1; right-hand pair treated on leaf no. 4. 

 Dosage, 0.05 fiC. Treatment time, 24 hrs. 



