Application and Persistence 191 



Carriers are often very helpful in applying auxin solutions to 

 foliage. Some examples of such carriers are carbowax (a mixture of 

 polyalkalene glycols), detergents, or wettable powders. Employment of 

 carriers not only permits the use of high concentrations of auxins, but 

 also can increase the absorption of the materials into the plant tissues. 

 This effect on absorption has been discussed in chapter VI. 



Instead of organic carriers, emulsions are sometimes utilized, such 

 as the lanolin emulsion described by Wi throw and Hewlett (1946) 

 consisting of stearic acid, lanolin and water. Such elaborate prepara- 

 tions are not in wide use now, however, since the advent of good 

 organic carriers for water solutions. 



A helpful means of applying growth regulator sprays is with a 

 freon or aerosol bomb type dispenser. For this purpose, the growth 

 regulator is used as an ester derivative, since such derivatives are 

 soluble in the freon solution, whereas most other derivatives are 

 insoluble. 



Instead of true solutions, auxins are often applied as pastes or 

 talcs. The commonest type of auxin paste in use today is the lanolin 

 paste in which a purified lanolin is simply melted over a water bath 

 and the auxins are mixed in. It has been found that if the crystals 

 are directly dissolved into the lanolin a solution was obtained which 

 was ten times less effective than if the crystals were first dissolved in 

 a small amount of alcohol or ether (Michel, 1951). Redemann et al 

 (1950) expressed the additional caution that some crude lanolin pastes 

 are capable of oxidizing indoleacetic acid and, for that reason, a 

 purified lanolin is recommended. Talc dusts are commonly employed 

 in the rooting of cuttings. To prepare such dusts one simply dissolves 

 the auxin crystals in a small amount of alcohol or ether and mixes 

 it thoroughly with talc to make a paste. After the auxin and talc have 

 been intimately mixed together, the solvent is evaporated off, and 

 the dry talc preparation is left. 



METHODS OF APPLICATION 



A wide variety of techniques has been developed for applying 

 auxins to growing plants. These may be grouped into four categories: 

 a) spraying solutions on the foliage, b) infiltration into leaves, c) in- 

 jection into fleshy parts, and d) the immersion of plant parts into 

 auxin solutions. 



A direct spray on the foliage is the simplest method of application, 

 but has some disadvantages in that the effective quantity of auxin is 

 not well controlled. The effectiveness of foliage sprays may be strongly 

 influenced by the ability of the auxin to penetrate through the cuticle 



