PLANT HORMONES 



209 



Table 25. Comparative Activity of Phenoxy and Substituted Phenoxy Derivatives of 

 the Lower Fatty Acids. Tested as Lanolin Preparations 



The simplest method knowTi for testing new chemicals is by means of 

 the lanoHn preparation made by mixing 10 to 20 mg of the substance ^\^th 

 one gram of lanolin. When these are thoroughly mixed, a small amount is 

 applied with a glass rod to the upper side of a young tomato leaf and to 

 one side of the adjacent stem. The angle between the stem and the leaf 

 before treatment is usually near 45 degrees. If the chemical is active, 

 causing cell elongation, the leaf moves downward and the stem curves away 

 from the treated side, thus increasing the degree of the angle (Fig. 75). 

 The same plant is kept for 10 to 12 days to determine the effect on cell 

 division, root-inducing activity, and formative effects. If activity is indi- 

 cated by the first test, the chemicals are then studied in comparison with 

 a standard, such as a-naphthaleneacetic acid, which is active when used at 

 0.001 per cent in lanolin. 



Comparisons can also be made by applying the chemical to the soil of the 

 potted plant. For example, 1 to 10 mg of an active chemical in 50 cc of 

 water applied to the soil will cause the entire plant to show an epinastic 

 response. This then is usually followed by the three other responses 

 described above. 



Induction of adventitious roots. To date practically all the recorded 

 growth substances which induce cell elongation (causing epinasty or stem 

 curvatures) are active also for inducing adventitious roots. This capacity 

 may be associated with the power to induce cell division. It is a fact that 

 growth substances which induce mature cells to make further growth also 



