A. S. CRAFTS 



University of California, Davis 



Improvement of Growth Regulator Formulation 



In the use of growth regulators we are constantly attempting to ob- 

 tain maximum effectiveness from minimum dosage. This high effi- 

 ciency is desirable from two standpoints: first, economy, and second, 

 distribution. Economy may or may not be important. With chemi- 

 cals such as the indole derivatives cost is an appreciable factor; with 

 2,4-D and other phenoxy compounds used as regulators, the price 

 is so low that cost is only nominal. 



Distribution within the plant is essential to the function of most 

 growth regulators which, by definition, act at a distance from the 

 point of application. And with regulators used as herbicides distri- 

 bution is imperative, as in the control of perennials from foliar ap- 

 plication. In such use we are faced with the paradox of requiring 

 living cells of the phloem to conduct a toxic chemical through leaves 

 and stems at concentrations that must, possibly after some local ac- 

 cumulation, prove lethal in roots. 



In the foliar application of regulators there are two mechanisms 

 of uptake into the living mesophyll, cuticular and stomatal. However, 

 the differences between these are not basic but rather relative. That 

 is, cuticular absorption involves movement across a relatively thick 

 fatty layer from an environment that may have a low relative humid- 

 ity whereas stomatal absorption involves uptake across cell walls hav- 

 ing a thin cuticle from an environment approaching water saturation. 

 Both include diffusion of the chemical across cells walls, partition to 

 the cytoplasm, and migration via the symplast to the vascular tissues. 



Earlier work with dinitro compounds and pentachlorophenol (2) 

 proved that buffering the spray solution on the acid side greatly in- 

 creased penetration of the chemicals. This has been taken to indi- 



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