238 



GROWTH OF PLANTS 



average only 2 grams of thiourea in a year. Only a minor fraction of these 

 crops would ever be treated with any antioxidants. The chances are poor 

 that any individual would get as much as a gram of thiourea in a year by 



Figure 90. Inducing dormancy in potato tubers with the potassium salt of a-naph- 

 thaleneacetic acid and then breaking it with ethylene chlorhydrin. A, Pieces treated 

 with the potassium salt of a-naphthaleneacetic acid, 100 mg per liter for 4 days. B, Con- 

 trol pieces treated with water. C, Pieces hke those shown in A treated with ethylene 

 chlorhydrin, 24 hr. dip, 25 cc of 40 per cent per Uter. D, Pieces hke those in A, treated 

 with water. 



eatmg fruit treated with it. A year's dose from treated fruit would be less 

 than a daily dose for goitrogenic or therapeutic effects and is far below the 

 threshold for either goitrogenic or therapeutic effects. In spite of these 

 facts the United States Food and Drug Administration prohibits the use 

 of thiourea as an antioxidant on fruit. 



