218 



GROWTH OF PLANTS 



Fruit set and seedless fruit. A long list of growth substances capable of 

 causing fruit set A\dthout pollination of the flower is given m Table 26. In 

 addition to inducing seedless fruit (Fig. 81), these chemicals may, under 

 certam conditions, increase the size of fruit resulting from pollinated 



Table 26. Growth Substances Active for Parthenocarpy, Fruit Set of Tomatoes, and 

 Activity or Inactivity for Modification of Leaves. Applied as Spray to Flower Clusters 



Phenoxy acids 



Q:-(Phenoxy)-propionic acid 

 a-(Phenoxy)-n-butyric acid 

 2-Chlorophenoxyacetic acid 

 Of- (2-Chlorophenoxy)-propionic acid 

 a-(2-Chlorophenoxy)-n-butyric acid 

 a-(2-Methylphenoxy)-propionic acid 

 a-(3-Chlorophenoxy)-propioiiic acid 

 a- (3-Chlorophenoxy )-n-butyric acid 

 4-Chloroj)henoxyacetic acid 

 a-(4-Chlorophenoxy)-propionic acid 

 a-(4-Chlorophenoxy)-w-butyric acid 

 2,4-Dichlorophenoxyacetic acid 

 a-(2,4-Dichlorophenoxy)-propionic acid 

 a-(2,4-Dichlorophenoxy)-n-butyric acid 

 2,4-Dimethylphenoxyacetic acid 

 a-(2,4-Dimethylphenoxy)-propionic acid 

 2,5-Dichlorophenoxyacetic acid 

 a-(2,5-Dimethylphenoxy)-propionic acid 

 a-(2,5-Dimethylphenoxy)-n-butyric acid 

 3,4-Dimethylphenoxyacetic acid 

 a-(3,4-Dimethylphenoxy)-propionic acid 

 2,4,5-Trichlorophenoxyacetic acid 

 a-(2,4,5-Trichlorophenoxy)-propionic acid 

 a-(2,4,5-Trichlorophenoxy)-n-butyric acid 

 2,4,5-Triniethylphenoxyacetic acid 

 2,4,6-Trichlorophenoxyacetic acid 

 /^-(2,4,6-Trichlorophenoxy)-/3'-chlorodiethyl ether 

 /3-Naphthoxyacetic acid 

 /3-Naphthoxypropionic acid 

 /3-Indolebutyric acid 

 2,5-Dichlorobenzoic acid 



Effective range 



of concentrations 



for fruit set in 



mg/1 of water 



100-200 



100-200 



200-300 



25-50 



50-200 



50-100 



50-200 



Active 



50-100 



50-200 



50-200 



5-10 



50-100 



50-100 



300-450 



300-450 



25-100 



100-300 



Active 



Active 



300-500 



25-100 



10-50 



25-100 



25-100 



Active 



Active 



50-100 



50-100 



500-1,000 



100-300 



Activity or 



inactivity for 



modification of 



leaves 



Active 



Active 



Active 



Inactive 



Inactive 



Inactive 



Inactive 



Inactive 



Active 



Inactive 



Inactive 



Active 



Inactive 



Inactive 



Active 



Active 



Inactive 



Inactive 



Inactive 



Active 



Active 



Inactive 



Inactive 



Inactive 



Active 



Active 



Active 



Active 



Active 



Inactive 



Active 



flowers.^' " In the latter case the resultmg fruit may be partially seedless, 

 but once the eggs are fertilized the substances do not inhibit their growth. 

 Under certain conditions only the wall of the fruit may be stimulated by 

 the chemical; as a result, it develops more rapidly than the gelatmous 

 pulp. When this happens there may be a space between the pulp and the 

 wall. Although the flavor of the fruit may not be impaired, this condition 

 makes the fruit unsatisfactory for commercial purposes. 



Several methods for applying growth substances to tomato flowers have 

 been developed. Perhaps the simplest is the application of spray to the 



